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walk through the logical framework (LogFrame) and to create the project management documents needed to successfully lead a project.General requirements:
Reread the Kitchen Heaven Project Case Study in Heldman et al. pages 84-87, 139-141, and 283-285 and read pages 190-193.
Part 1: Action Steps Column (A)
Part 2: Project Life-Cycles
Chapter
4
Creating the Project
Schedule
The PMP® exam content from the
Planning performance domain covered
in this chapter includes the following:
✓✓ Task 4: Develop the project schedule based on the
approved project deliverables and milestones, scope, and
resource management plans in order to manage timely
completion of the project.
✓✓ Knowledge and Skills:
■■
Time management planning, including scheduling tools and
techniques
Workflow diagramming techniques
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■■
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Copyright © 2015. John Wiley & Sons, Incorporated. All rights reserved.
The Planning process group has more processes than any
other process group. As a result, a lot of time and effort goes
into the Planning processes of any project. On some projects,
you might spend almost as much time planning the project as you do executing and
controlling it. This isn’t a bad thing. The better planning you do up front, the more likely
you’ll have a successful project. Speaking of planning, together the Planning, Executing,
and Monitoring and Controlling process groups account for almost 70 percent of the PMP ®
exam questions, so plan on spending about the same percentage of your study time on these
areas.
This is another fun‐filled, action‐packed chapter. We’ll start off by defining the
schedule management plan and then move on to the activities that become the work of
the project. The WBS will come in handy here, so keep it close. Then we’ll sequence the
activities in their proper order, estimate the resources we’ll need to complete the work,
and estimate how long each activity will take. Last but not least, we’ll develop the project
schedule.
Everything you’ve done up to this point and the processes we’ll discuss in this chapter
will help you create an accurate project schedule. You’ll use these documents (along with
several other documents you’ve created along the way) throughout the Executing and
Monitoring and Controlling processes to help measure the progress of the project. Let’s get
going.
The process names, inputs, tools and techniques, outputs, and
descriptions of the project management process groups and related
materials and figures in this chapter are based on content from A Guide to
the Project Management Body of Knowledge (PMBOK® Guide), Fifth Edition
(PMI, 2013).
Creating the Schedule
Management Plan
The Plan Schedule Management process describes how the project schedule will be
developed, executed, and controlled as well as how changes will be incorporated into the
project schedule. According to A Guide to the Project Management Body of Knowledge
(PMBOK® Guide), Fifth Edition, the primary benefit of this process is that it helps guide
Heldman, Kim. PMP: Project Management Professional Exam Study Guide : Updated for the 2015 Exam, John Wiley & Sons, Incorporated, 2015. ProQuest
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Creating the Schedule Management Plan
153
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and direct how the project schedule will be managed. The only output of this process is
the schedule management plan. Let’s first look at the inputs and the tools and techniques
of this process and spend most of our time examining the schedule management
plan itself.
The inputs of this process include the project management plan, project charter,
enterprise environmental factors, and organizational process assets. The project
management plan includes the scope baseline, which in turn is made up of the project
scope statement, WBS, and WBS dictionary. The project schedule will be derived from the
WBS (which includes deliverables and work package levels), so the scope baseline is key to
defining the processes you’ll use to develop the schedule management plan.
Enterprise environmental factors include the culture of the organization and availability
of resources as well as the project management software and work authorization system
the organization uses to assign and track work components. The organizational process
assets that are important to this process are templates, change control processes, historical
information, policies and guidelines for schedule control, control tools for managing
schedules, and risk control processes and procedures.
We have seen all of the tools and techniques before. They are expert judgment,
analytical techniques, and meetings.
The key to this process, as I stated earlier, is the schedule management plan, which
is an element of the project management plan. It is the only output of this process, and
it serves to describe how the project schedule will be developed, monitored, controlled,
and changed. According to the PMBOK® Guide, several elements make up the schedule
management plan. Be certain to review all of them. I have highlighted the most important
elements here:
Schedule Model Development This refers to the methodologies and tools you’ll use to
develop the schedule (for example, Oracle Primavera or Microsoft Project), along with the
data they contain.
Accuracy Levels This element describes the rounding you’ll use when deriving activity
duration estimates. For example, you might round to the nearest week, day, or hour
depending on the complexity of the project.
Units of Measure This element also concerns activity duration estimates as well as
schedule activities. This describes what measure you’ll use when developing the schedule,
such as hours, days, weeks, or some other measure.
Control Thresholds Control thresholds refer to the level of variance the schedule can
experience before you take action. Again, depending on the complexity of the project, this
might be a generous amount of time or a very limited amount of time. You can express
thresholds in terms of hours or days (as an example, a slippage of greater than three days
requires action) or, most typically, as a percentage of time.
Performance Measurement Rules This refers to where and what types of measures you’ll
use to verify schedule performance. This could include designating levels on the WBS and/
or determining what type of earned value measurement technique you’ll use.
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154
Chapter 4
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Creating the Project Schedule
Defining Activities
Now you’re off and running toward the development of your project schedule. To develop
the schedule, you first need to define the activities, sequence them in the right order,
estimate resources, and estimate the time it will take to complete the tasks. I’ll cover the
Define Activities process here and the Sequence Activities process next, and I’ll pick up
with the estimating processes in the next chapter.
Define Activities and Sequence Activities are separate processes, each
with its own inputs, tools and techniques, and outputs. In practice,
especially for small to medium‐sized projects, you can combine the Create
WBS process we talked about in Chapter 3, “Developing the Project Scope
Statement,” with these processes and complete them all at once.
The Define Activities process is a further breakdown of the work package elements
of the WBS. It documents the specific activities needed to fulfill the deliverables detailed
on the WBS and the project scope statement. Much as with the work package level of the
WBS, activities can be easily assigned, estimated, scheduled, and controlled. The Define
Activities process might be performed by the project manager, or when the WBS is broken
down to the subproject level, this process (and all the activity‐related processes that follow)
might be assigned to a subproject manager.
Copyright © 2015. John Wiley & Sons, Incorporated. All rights reserved.
Define Activities Process Inputs
The following are inputs (including the key elements of each input) to the Define Activities
process:
■■
Schedule management plan
■■
Scope baseline (including deliverables, constraints, and assumptions)
■■
■■
Enterprise environmental factors (project management information systems,
organizational culture, published commercial databases)
Organizational process assets (existing guidelines and policies, templates, lessons
learned knowledge base, and historical information)
Tools and Techniques for Defining Activities
The tools and techniques of the Define Activities process are as follows:
■■
Decomposition
■■
Rolling wave planning
■■
Expert judgment
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Defining Activities
155
We covered most of these topics in the previous chapter. Decomposition in this process
involves breaking the work packages into smaller, more manageable units of work
called activities. These are not deliverables but the individual units of work that must be
completed to fulfill the work packages and the deliverables listed in the WBS. Activities will
help in later Planning processes to define estimates and create the project schedule. Activity
lists (which are one of the outputs of this process) from prior projects can be used as
templates in this process. Rolling wave planning involves planning near‐term work in more
detail than future‐term work. As we discussed in Chapter 3, this is a form of progressive
elaboration. Expert judgment, in the form of project team members with prior experience
developing project scope statements and WBSs, can help you define activities.
Exam Spotlight
The purpose of the Define Activities process is to decompose the work packages into
schedule activities where the basis for estimating, scheduling, executing, and monitoring
and controlling the work of the project is easily supported and accomplished.
Define Activities Outputs
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Define Activities has three outputs:
■■
Activity list
■■
Activity attributes
■■
Milestone list
We’ll look at each of these outputs next.
Activity List
One primary output of the Define Activities process is an activity list. The activity list
should contain all the schedule activities that will be performed for the project, with a
scope of work description of each activity and an identifier (such as a code or number)
so that team members understand what the work is and how it is to be completed. The
schedule activities are individual elements of the project schedule, and the activity list
document is part of the project documents. To keep your sanity, and that of your team
members, make certain to enter the activity names onto the schedule the same way they
appear on the activity list.
Activity Attributes
Activity attributes describe the characteristics of the activities and are an extension of the
activity list. Activity attributes will change over the life of the project as more information
is known. In the early stages of the project, activity attributes might include the activity ID,
the WBS identification code it’s associated with, and the activity name. As you progress
Heldman, Kim. PMP: Project Management Professional Exam Study Guide : Updated for the 2015 Exam, John Wiley & Sons, Incorporated, 2015. ProQuest
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156
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through the project and complete other Planning processes, you might add predecessor
and successor activities, logical relationships, leads and lags, resource requirements,
and constraints and assumptions associated with the activity. We’ll cover these topics
throughout the remainder of this chapter.
The activity attributes are used as input to several processes, including the Develop
Schedule process that we’ll talk about in the section “Developing the Project Schedule”
later in this chapter.
In practice, I like to tie the activity list to the WBS. Remember from Chapter 3
that each WBS element has a unique identifier, just like the activities in the
activity list. When recording the identifier code for the activity list, I’ll use a
system whereby the first three or four digits represent the WBS element the
activity is tied to and the remaining digits refer to the activity itself.
Milestone Lists
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Milestones are typically major accomplishments of the project and mark the completion
of major deliverables or some other key event in the project. For example, approval and
sign‐off on project deliverables might be considered milestones. Other examples might be
the completion of a prototype, system testing, contract approval, and so on. The milestone
list records these accomplishments and documents whether the milestone is mandatory or
optional. The milestone list is part of the project documentation and is also used to help
develop the project schedule.
Understanding the Sequence
Activities Process
Now that you’ve identified the schedule activities, you need to sequence them in a logical
order and find out whether dependencies exist among the activities. The interactivity of
logical relationships must be sequenced correctly in order to facilitate the development of a
realistic, achievable project schedule.
Consider a classic example. Let’s say you’re going to paint your house, but unfortunately,
it’s fallen into a little disrepair. The old paint is peeling and chipping and will need to be
scraped before a coat of primer can be sprayed on the house. After the primer dries, the
painting can commence. In this example, the primer activity depends on the scraping. You
can’t—okay, you shouldn’t—prime the house before scraping off the peeling paint. The
painting activity depends on the primer activity in the same way. You really shouldn’t start
painting until the primer has dried.
During Sequence Activities, you will use a host of inputs and tools and techniques to
produce the primary output and project schedule network diagrams. You’ve already seen
Heldman, Kim. PMP: Project Management Professional Exam Study Guide : Updated for the 2015 Exam, John Wiley & Sons, Incorporated, 2015. ProQuest
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Understanding the Sequence Activities Process
157
all the inputs to this process. They are the schedule management plan, activity list, activity
attributes, milestone list, project scope statement, enterprise environmental factors, and
organizational process assets. We’ll look at several new tools and techniques next.
Sequence Activities Tools and Techniques
Sequence Activities has three tools and techniques, all of which are new to you:
■■
Precedence diagramming method (PDM)
■■
Dependency determination
■■
Leads and lags
I’ll switch the order of these and cover dependency determination first. In practice, you’ll
define dependencies either before or while you’re using the PDM to draw your schedule
network. To make sure you’re on the same page with the PMBOK® Guide terminology
regarding dependencies, I’ll cover them first and then move on to the other tools and
techniques.
Dependency Determination
Copyright © 2015. John Wiley & Sons, Incorporated. All rights reserved.
Dependencies are relationships between the activities in which one activity is dependent on
another to complete an action, or perhaps an activity is dependent on another to start an
action before it can proceed. Dependency determination is a matter of determining where
those dependencies exist. Thinking back to the house‐painting example, you couldn’t paint
until the scraping and priming activities were completed. You’ll want to know about four
types of dependencies for the exam:
■■
Mandatory dependencies
■■
Discretionary dependencies
■■
External dependencies
■■
Internal dependencies
As you’ve probably guessed, the PMBOK® Guide defines dependencies differently
depending on their characteristics:
Mandatory Dependencies Mandatory dependencies, also known as hard logic or hard
dependencies, are defined by the type of work being performed. The scraping, primer, and
painting sequence is an example of mandatory dependencies. The nature of the work itself
dictates the order in which the activities should be performed. An activity with physical
limitations is a telltale sign that you have a mandatory dependency on your hands.
Discretionary Dependencies Discretionary dependencies are defined by the project team.
Discretionary dependencies are also known as preferred logic, soft logic, or preferential
logic. These are usually process‐ or procedure‐driven or “best‐practice” techniques based
on past experience. For example, both past experience and best practices on house‐painting
projects have shown that all trim work should be hand‐painted whereas the bulk of the
main painting work should be done with a sprayer.
Heldman, Kim. PMP: Project Management Professional Exam Study Guide : Updated for the 2015 Exam, John Wiley & Sons, Incorporated, 2015. ProQuest
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Exam Spotlight
Discretionary dependencies have a tendency to create arbitrary total float values that will
limit your options when scheduling activities that have this type of dependency. If you
are fast tracking to compress your schedule, you should consider changing or removing
these dependencies.
External Dependencies External dependencies are, well, external to the project. This
might seem obvious, but the PMBOK® Guide points out that even though the dependency
is external to the project (and, therefore, a nonproject activity), it impacts project activities.
For example, perhaps your project is researching and marketing a new drug. The FDA must
approve the drug before your company can market it. This is not a project activity, but
the project cannot move forward until approval occurs. That means FDA approval is an
external dependency.
Copyright © 2015. John Wiley & Sons, Incorporated. All rights reserved.
Internal Dependencies Internal dependencies, another somewhat obvious dependency,
are internal to the project or the organization. They may, however, still be outside of your
control. For example, perhaps before implementing a new time tracking system in your
maintenance shop, the operations department has decided to study the business rules
regarding time tracking. Examining and updating the business rules and processes needs to
be completed before the time tracking system can be installed and your project can proceed.
Once you’ve identified the dependencies and assembled all the other inputs for the Sequence
Activities process, you’ll take this information and produce a diagram—or schematic display—
of the project activities. The project schedule network diagram shows the dependencies—or
logical relationships—that exist among the activities. You can use one of the other tools and
techniques of this process to produce this output. You’ll now examine each in detail.
Precedence Diagramming Method (PDM)
The precedence diagramming method (PDM) is what most project management software
programs use to sequence activities. Precedence diagrams use boxes or rectangles (called
nodes) to represent the activities. The nodes are connected with arrows showing the
dependencies between the activities. This method is also called activity on node (AON).
The minimum information that should be displayed on the node is the activity name, but
you might put as much information about the activity on the node as you’d like. Sometimes
the nodes are displayed with activity name, activity number, start and stop dates, due
dates, slack time, and so on. (I’ll cover slack time in the section “Develop Schedule Tools
and Techniques” later in this chapter.)
Exam Spotlight
For the exam, remember that the PDM uses only one time estimate to determine duration.
Heldman, Kim. PMP: Project Management Professional Exam Study Guide : Updated for the 2015 Exam, John Wiley & Sons, Incorporated, 2015. ProQuest
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Understanding the Sequence Activities Process
159
Figure 4.1 shows a PDM—or AON—of the house‐painting example.
F i g u r e 4 .1
Example of a PDM or AON
Project
Start
Scrape
Prime
Paint
Finish
Clean
Equipment
The PDM is further defined by four types of logical relationships. The terms dependencies
and precedence relationships also are used to describe these relationships. You might
already be familiar with these if you’ve used Microsoft Project or similar project
management software. The four dependencies, or logical relationships, are as follows:
Finish‐to‐Start (FS) The finish‐to‐start relationship is the most frequently used
relationship. This relationship says that the predecessor—or from activity—must finish
before the successor—or to activity—can start. In PDM diagrams, this is the most often
used logical relationship.
Start‐to‐Finish (SF) The start‐to‐finish relationship says that the predecessor activity must
start before the successor activity can finish. This logical relationship is seldom used.
Copyright © 2015. John Wiley & Sons, Incorporated. All rights reserved.
Finish‐to‐Finish (FF) The finish‐to‐finish relationship says that the predecessor activity
must finish before the successor activity finishes.
Start‐to‐Start (SS) I think you’re getting the hang of this. The start‐to‐start relationship
says that the predecessor activity must start before the successive activity can start.
Exam Spotlight
For the exam, know that finish‐to‐start is the most commonly used dependency in the
PDM method and that start‐to‐finish is rarely used. Also remember that according to the
PMBOK® Guide, each activity and/or milestone on the network diagram is connected
by either at least one predecessor and/or a successor activity except the first and last
activity and/or milestone.
Keep these logical relationships (or dependencies) in mind when constructing your
project schedule network diagram.
Other Diagramming Methods
The arrow diagramming method (ADM) is not a listed tool and technique of the Sequence
Activities process, but there is a possibility you could see a question on the exam regarding
Heldman, Kim. PMP: Project Management Professional Exam Study Guide : Updated for the 2015 Exam, John Wiley & Sons, Incorporated, 2015. ProQuest
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160
Chapter 4
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it. It’s an old technique that’s rarely used anymore, but nonetheless you should have some
familiarity with it.
The ADM is visually the opposite of the PDM. The arrow diagramming method places
activities on the arrows, which are connected to dependent activities with nodes. This
method is also called activity on arrow (AOA) and activity on line (AOL). This technique
isn’t used nearly as often as the PDM, but some industries prefer the ADM to the PDM. For
the record, note that the ADM allows for more than one time estimate to determine duration
and uses only the finish‐to‐start dependency. There’s one more unique note about the ADM
to tuck away: Sometimes dummy activities must be plugged into the diagram to accurately
display the dependencies. Dummy activities are commonly depicted using a dotted arrow.
Figure 4.2 shows the ADM method applied to the house‐painting example.
Figure 4.2
Example of an ADM method
Start
Scrape
Prime
Clean Equipment
Paint
Finish
Remove Masking
Exam Spotlight
I recommend that you memorize the following graphic to help you remember the tools
and techniques of the Sequence Activities process and their characteristics for the exam.
Copyright © 2015. John Wiley & Sons, Incorporated. All rights reserved.
PDM = AON = 1 Time Estimate
Activity
On Node
ADM = AOA => 1 Time Estimate
Activity
On Arrow
This might look a little strange, but I think it will work for you now that you understand
what each of these diagramming methods is. This is information you need to know for
the exam. If this graphic isn’t useful for you, come up with your own mnemonic or sample
that will help you remember which of these is which. Don’t say I didn’t warn you.
There is one other diagramming method you could potentially see a question about on
the exam. It’s called GERT, which stands for Graphical Evaluation and Review Technique.
Heldman, Kim. PMP: Project Management Professional Exam Study Guide : Updated for the 2015 Exam, John Wiley & Sons, Incorporated, 2015. ProQuest
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Understanding the Sequence Activities Process
161
What you should know for the exam is that this diagramming method allows for
conditions, branches, and loops.
Applying Leads and Lags
Leads and lags should be considered when determining dependencies. Lags occur when
time elapses between two activities, which delays successor activities (those that follow a
predecessor activity) from starting, and as a result, time is added either to the start date or
to the finish date of the activity you’re scheduling. Leads, conversely, speed up the successor
activities, and as a result, time needs to be subtracted from the start date or the finish date
of the activity you’re scheduling.
Exam Spotlight
Copyright © 2015. John Wiley & Sons, Incorporated. All rights reserved.
Leads and lags speed up or delay successor activities but should not replace schedule
logic.
Let’s revisit the house‐painting example to put all this in perspective. In order to paint,
you first need to scrape the peeling paint and then prime. However, you can’t begin
painting until the primer has dried, so you shouldn’t schedule priming for Monday and
painting for Tuesday if you need the primer to dry on Tuesday. Therefore, the priming
activity generates the need for lag time at the end of the activity to account for the drying
time needed before you can start painting.
Lead time works just the opposite. Suppose, for this example, you could start priming
before the scraping is finished. Maybe certain areas on the house don’t require scraping, so
you don’t need to wait until the scraping activity finishes to begin the priming activity. In
this example, lead time is subtracted from the beginning of the priming activity so that this
activity begins prior to the previous activity finishing.
You might also use schedule network templates in this process. These are
not a named tool and technique of this process but may come in handy on
your next project. Schedule network templates are like the templates I’ve
talked about in previous processes. Perhaps the project you’re working on
is similar to a project that has been completed in the past. You can use a
previous project schedule network diagram as a template for the current
project. Or you might be working on a project with several deliverables
that are fairly identical to projects you’ve performed in the past or the
deliverables on the existing project are fairly similar; in that case, you
can use the old schedule network diagrams, or even the same schedule
network diagrams, as templates for the project. Templates can be used for
certain portions of the project schedule or for the entire project. If you are
using templates for portions of the project schedule, they are known as
subnetwork templates or fragment network templates.
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Sequence Activities Outputs
There are only two outputs of the Sequence Activities process: project schedule network
diagrams and project documents updates. I’ve just spent a good deal of time describing the
different types of project schedule network diagrams you can construct using the PDM or
ADM techniques. You can generate project schedule network diagrams on a computer, or
you can draw them by hand. Like the WBS, these diagrams are visual representations of
the work of the project and might contain all the project details or they might contain only
summary‐level details, depending on the complexity of the project. Summary‐level activities
are a collection of related activities, also known as hammocks. Think of hammocks as a
group of related activities rolled up into a summary heading that describes the activities
likely to be contained in that grouping.
Keep in mind that the construction of these project schedule network diagrams might
bring activities to light that you missed when defining your activity list, or it might make
you break an activity down into two activities in places where you thought one activity
might work. If this is the case, you will need to update the activity list and the activity
attributes. The other project document update that may be required as a result of this
process is an update to the risk register. (We’ll talk about the risk register in Chapter 6,
“Risk Planning.”)
After the activities are sequenced, the next steps involve estimating the resources and
estimating the durations of the activities so that they can be plugged into the project
schedule. We’ll look at these topics in the next sections of this chapter.
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Estimating Activity Resources
All projects, from the smallest to the largest, require resources. The term resources, in this
case, does not mean just people; it means all the physical resources required to complete
the project. The PMBOK® Guide defines resources as people, equipment, materials,
and supplies. In reality, this includes people, equipment, supplies, materials, software,
hardware—the list goes on depending on the project on which you’re working. The
Estimate Activity Resources process is concerned with determining the types of resources
needed (both human and materials) and in what quantities for each schedule activity within
a work package.
Remember, the activity resource requirements output from the Estimate
Activity Resources process is an input to the Plan Human Resource
Management process.
The PMBOK® Guide notes that Estimate Activity Resources should be closely coordinated
with the Estimate Costs process (I’ll talk about Estimate Costs in Chapter 5, “Developing the
Project Budget and Communicating the Plan”). That’s because resources—whether people or
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Estimating Activity Resources
163
material or both—are typically the largest expense you’ll have on any project. Identifying the
resources becomes a critical component of the project planning process so estimates—and
ultimately the project budget—can be accurately derived. You’ll look at the inputs and tools
and techniques that will help you document these requirements next.
Estimate Activity Resources Inputs
The Estimate Activity Resources process has several inputs, most of which you already
know:
■■
Schedule management plan
■■
Activity list
■■
Activity attributes
■■
Resource calendars
■■
Risk register
■■
Activity cost estimates
■■
Enterprise environmental factors
■■
Organizational process assets
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The only inputs you haven’t seen before are resource calendars, risk register, and activity
cost estimates.
Resource calendars are an output of the Acquire Project Team and Conduct
Procurements processes. Both of these processes are performed during
the Executing process group, so you may find this input perplexing here.
However, you may have some resource availability information (resource
calendars) on a preliminary basis during the Estimate Activity Resources
process, and you’ll further define it when resources are assigned to the
project later in the Executing processes. In practice, you may find that you
perform the Acquire Project Team process during the later stages of the
Planning portion of the project rather than in the Executing process.
The resource calendars input describes the time frames in which resources (both human
and material) are available. They look at a particular resource or groups of resources and
their skills, abilities, quantity, and availability. Perhaps your project calls for a marketing
resource and the person assigned to the marketing activities is on an extended vacation in
October. The resource calendar would show this person’s vacation schedule. (The overall
project calendar shows the holidays the company recognizes.)
Resource calendars also examine the quantity, capability, and availability of equipment
and material resources that have a potential to impact the project schedule. For example,
suppose your project calls for a hydraulic drill and your organization owns only one. The
resource calendar will tell you whether it’s scheduled for another job at the same time it’s
needed for your project.
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The risk register is an output of the Identify Risks process. It is a list of identified risks
and their potential responses. We will discuss the risk register in more depth in Chapter 6,
“Risk Planning.”
Activity cost estimates are an output of the Estimate Costs process. These are the costs
that are determined for each activity. We will look at activity cost estimates in more depth
in Chapter 5.
Estimate Activity Resources Tools and Techniques
Your goal with the Estimate Activity Resources process is to determine the activity resource
requirements, including quantity and availability. This process has five tools and techniques
to help accomplish this output: expert judgment, alternative analysis, published estimating
data, bottom‐up estimating, and project management software. You already know what
expert judgment entails, so take a look at the remaining tools:
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Alternative Analysis Alternative analysis is used when thinking about the methods you
might use to accomplish the activities your resources have been assigned. Many times,
you can accomplish an activity in more than one way, and alternative analysis helps
decide among the possibilities. For example, a subcompact car drives on the same roads a
six‐figure sports car travels. The sports car has a lot more features than the subcompact,
it’s faster, it’s probably more comfortable, and it has a visual appeal that the subcompact
doesn’t. The sports car might be the valid resource choice for the project, but you should
consider all the alternatives. The same idea applies to human resources in that you might
apply senior‐level resources versus junior‐level resources, or you could add resources to
speed up the schedule. You may also use make‐rent‐or‐buy analysis when determining
alternative resources.
Published Estimating Data Estimating data might include organizational guidelines,
industry rates or estimates, production rates, resource rates, and so on. For example, your
organization might have established price agreements with vendors that outline rates by
resource types, or there might be industry estimates for production rates for your particular
activity or your particular geographical region.
Bottom‐Up Estimating Bottom‐up estimating is a process of estimating individual
schedule activity costs and then adding them together to come up with a total estimate for
the work package. Here you estimate every schedule activity individually and then roll up
those estimates, or add them all together, to come up with a total. This is an accurate means
of estimating, provided the estimates at the schedule activity level are accurate. However, it
takes a considerable amount of time to perform bottom‐up estimating because every activity
must be assessed and estimated accurately to be included in the bottom‐up calculation. The
smaller and more detailed the activity, the greater the accuracy and cost of this technique. If
it isn’t possible to estimate the activity cost, you’ll need to decompose the activity to a lower
level of detail so that an estimate can be performed. Bottom‐up estimating may also be used
to determine activity durations and is a good technique to use when you aren’t confident
about the type or quantity of resources you’ll need for the project.
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Project Management Software Project management software can help plan, organize, and
estimate resource needs and document their availability. It might also help you to produce
resource breakdown structures, resource rates, resource calendars, and availability.
Estimate Activity Resources Outputs
The purpose of the Estimate Activity Resources process is to develop the activity resource
requirements output. This output describes the types of resources and the quantity
needed for each activity associated with a work package. You should prepare a narrative
description for this output that describes how you determined the estimate, including the
information you used to form your estimate and the assumptions you made about the
resources and their availability.
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Work package estimates are derived by taking a cumulative total of all the
schedule activities within the work package.
You’ll use the activity resource requirements in the next process (Estimate Activity
Durations) to determine the length of time each activity will take to complete. That, of
course, depends on the quantity and skill level of the resources assigned, which is the
reason you estimate resources before you try to determine duration.
The two other outputs of this process are resource breakdown structure and project
documents updates.
The resource breakdown structure (RBS) is much like an organizational breakdown
structure, but the RBS lists the resources by category and type. You may have several
categories of resources, including labor, hardware, equipment, supplies, and so on. Type
describes the types of resources needed, such as skill levels or quality grades of the material
and so on.
The project documents updates portion of this output refers to updating the activity list,
activity attributes, and the resource calendars with changes to any of the elements you’ve
recorded here.
You can see how these “Activity” processes have built on each other. First you defined
the activities, then you determined dependencies and sequenced them in the correct order,
and next you determined what types and quantities of resources are required to complete
the activities. Now you’re ready to begin estimating the duration of these activities so you
can plug them into the project schedule.
Estimating Activity Durations
The Estimate Activity Durations process attempts to estimate the work effort, resources,
and number of work periods needed to complete each activity. The activity duration
estimates are the primary output of this process. These are quantifiable estimates expressed
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as the number of work periods needed to complete a schedule activity. Work periods are
usually expressed in hours or days. However, larger projects might express duration in
weeks or months. Work periods are the activity duration estimates, and they become inputs
to the Develop Schedule process.
When estimating activity duration, be certain to include all the time that will elapse
from the beginning of the activity until the work is completed. For example, consider the
earlier example of the house‐painting project. You estimate that it will take three days,
including drying time, to prime the house. Now, let’s say priming is scheduled to begin
on Saturday, but your crew doesn’t work on Sunday. The activity duration in this case is
four days, which includes the three days to prime and dry plus the Sunday the crew doesn’t
work. Most project management software programs will handle this kind of situation
automatically once you’ve keyed in the project calendar and work periods.
Progressive elaboration comes into play during this process also. Estimates typically
start at a fairly high level, and as more details are known about the deliverables and their
associated activities, the estimates become more accurate. You should rely on those folks
who have the most knowledge of the activities you’re trying to estimate to help you with
this process.
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Estimate Activity Durations Inputs
The inputs to this process include the schedule management plan, activity list, activity
attributes, activity resource requirements, resource calendars, project scope statement,
risk register, resource breakdown structure, enterprise environmental factors, and
organizational process assets.
A few of the important elements regarding these inputs apply here as you’ve seen in
past processes: databases, productivity metrics, historical information regarding durations
on similar projects, project calendars, scheduling methodology, and lessons learned. The
project calendars (which list company holidays, shift schedules, and so on) are considered a
part of the organizational process assets, and activity resource requirements are especially
useful during this process.
Estimate Activity Durations Tools and Techniques
The Estimate Activity Durations process has several new tools and techniques:
■■
Expert judgment
■■
Analogous estimating
■■
Parametric estimating
■■
Three‐point estimating
■■
Group decision‐making techniques
■■
Reserve analysis
You’ll take a look at each of these tools and techniques next.
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Expert Judgment
The staff members who will perform activities will most accurately estimate them. In this
case, team members use expert judgment because of their experience with similar activities
in the past. You should be careful with these estimates, though, because they are subject to
bias and aren’t based on any scientific means. Your experts should consider that resource
levels, resource productivity, resource capability, risks, and other factors can impact
estimates. It’s good practice to combine expert judgment with historical information and
use as many experts as you can.
Copyright © 2015. John Wiley & Sons, Incorporated. All rights reserved.
Analogous Estimating
Analogous estimating, also called top‐down estimating, is a form of expert judgment.
With this technique, you will use the actual duration of a similar activity completed
on a previous project to determine the duration of the current activity—provided the
information was documented and stored with the project information on the previous
project. This technique is most useful when the previous activities you’re comparing are
similar to the activity you’re estimating and don’t just appear to be similar. You want
the folks who are working on the estimate to have experience with these activities so
they can provide reasonable estimates. This technique is especially helpful when detailed
information about the project is not available, such as in the early phases of the project.
Top‐down estimating techniques are also used to estimate total project duration,
particularly when you have a limited amount of information about the project. The best
way to think about top‐down techniques is to look at the estimate as a whole. Think about
being on a mountaintop where you can see the whole picture as one rather than all the
individual items that make up the picture.
For instance, let’s return to the house‐painting example. You would compare a previous
house‐painting project to the current house‐painting project if the houses are of similar
size and the paint you’re using is the same quality. You can use the first house‐painting
project to estimate the project duration for the second house‐painting project because of the
similarities in the project.
Top‐down techniques are useful when you’re early in the project Planning processes and
are just beginning to flesh out all the details of the project. Sometimes during the project
selection process, the selection committee might want an idea of the project’s duration. You
can derive a project estimate at this stage by using top‐down techniques.
Exam Spotlight
The PMBOK® Guide states that analogous estimating is a gross value estimating
technique. It also notes that you can use analogous estimating to determine overall
project duration and cost estimates for the entire project (or phases of the project). For
the exam, remember that the analogous technique is typically less time‐consuming and
less costly than other estimating techniques, but it’s also less accurate.
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Parametric Estimating
Parametric estimating is a quantitatively based estimating method that multiplies the
quantity of work by the rate or uses an algorithm in conjunction with historical data
to determine cost, budget, or duration estimates. The best way to describe it is with an
example. Suppose you are working on a companywide network upgrade project. This
requires you to run new cable to the switches on every floor in the building. To come
up with an estimate, you can use parametric estimates to determine activity duration
estimates by taking a known element—in this case, the amount of cable needed—and
multiplying it by the amount of time it takes to install a unit of cable. In other words,
suppose you have 10,000 meters of new cable to run. You know from past experience it
takes 1 hour to install 100 meters. Using this measurement, you can determine an estimate
for this activity of 100 hours to run the new cable. Therefore, the cable activity duration
estimate is 100 hours.
Exam Spotlight
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The PMBOK® Guide states that you can also use parametric estimating to determine
time estimates for the entire project or portions of the project when you are using this
technique in conjunction with other estimating techniques. For the exam, remember that
a statistical relationship exists between historical data and other variables (as explained
in the cable example earlier) when using parametric estimates and that this technique can
be highly accurate if the data you are using is reliable.
Three‐Point Estimating
Three‐point estimating, as you can probably guess, uses three estimates that, when
averaged, come up with a final estimate. The three estimates you’ll use in this technique
are the most likely estimate, an optimistic estimate, and a pessimistic estimate. The
most likely estimate assumes there are no disasters and the activity can be completed
as planned. The optimistic estimate is the fastest time frame in which your resource
can complete the activity. The pessimistic estimate assumes the worst happens and it
takes much longer than planned to get the activity completed. You’ll want to rely on
experienced folks to give you these estimates. Then you can choose to use one of two
formulas to calculate the expected duration estimate (E). The first formula, called the
triangular distribution, consists of summing the optimistic (O), the pessimistic (P),
and the most likely (M) estimates and then dividing that sum by 3. The formula looks
like this:
E = (O + P + M) / 3
The second formula is called a beta distribution, which is taken from the program
evaluation and review technique (PERT) that we will review in depth in the Develop
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Estimating Activity Durations
169
Schedule process later in this process. The formula for beta distribution, or PERT, looks
like this:
E = (O + P + 4M) / 6
Group Decision‐Making Techniques
Group decision‐making techniques include brainstorming and the Delphi or nominal group
techniques. These techniques get your team members involved and will help improve the
accuracy of your estimates. Brainstorming is an age‐old technique where all participants
have an opportunity to speak up. No idea is a bad idea with this technique, and it’s
essential that the facilitator not allow participants to get into judging contests or debates on
the merits of the ideas proposed during the brainstorming session.
The Delphi technique is similar to brainstorming in that you involve subject matter
experts in determining estimates. Their experiences with the organization and on similar
past projects will help improve the accuracy of the estimates. Because you have them
involved in the process and they know that the estimates derived from this exercise will
be attached to the project schedule, they are likely to provide more accurate estimates and
work hard to meet or beat them.
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Reserve Analysis
Contingency reserves—also called buffers or time reserves in the PMBOK® Guide—
means a portion of time (or money when you’re estimating budgets) that is added to
the schedule to account for risk or uncertainty. You might choose to add a percentage
of time or a set number of work periods to the activity or the overall schedule or both.
Contingency reserves are calculated for known risks that have documented contingency
or mitigation response plans to deal with the risk event should it occur, but you don’t
necessarily know how much time it will take to implement the mitigation plan and
potentially perform rework. For example, you know it will take 100 hours to run new
cable based on the quantitative estimate you came up with earlier. You also know that
sometimes you hit problem areas when running the cable. To make sure you don’t impact
the project schedule, you build in a reserve time of 10 percent of your original estimate to
account for the problems you might encounter. This brings your activity duration estimate
to 110 hours for this activity. Contingency reserves can be and should be modified as the
project progresses. As you use the time, or find you don’t need the time, you will modify
the reserve amounts.
Management reserves are a type of reserve used for unknown events. Since they are
unknown, you have not identified them as risks. Management reserves are for that funny
feeling you have that something could come up that you haven’t thought about during the
Planning process. Management reserves set aside periods of time for this unknown work
but are not included in the schedule baseline. Keep in mind this is not time that is available
to throw in extra deliverables that didn’t make it into the scope statement. Management
reserves must be used for project work that is within scope. If you do use management
reserves during the project, you must change the schedule baseline to reflect the time used.
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Exam Spotlight
Contingency reserves are included in the schedule baseline; management reserves are
not. Contingency reserves are for potential work identified during the Risk Planning
processes. Management reserves are for unknown circumstances that have not been
previously identified but require work that is within scope of the project. Management
reserves that are used on the project require a change to the schedule baseline.
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Estimate Activity Durations Outputs
Everything I’ve discussed to this point has brought you to the primary output of this
process: the activity duration estimates. You use the inputs and tools and techniques to
establish these estimates. As mentioned earlier, activity duration estimates are estimates of
the required work periods needed to complete the activity. This is a quantitative measure
usually expressed in hours, weeks, days, or months.
One factor to note about your final estimates as an output to this process is that they
should contain a range of possible results. In the cable‐running example, you would
state the activity duration estimates as “100 hours ± 10 hours” to show that the actual
duration will take at least 90 hours and might go as long as 110 hours—or you could use
percentages to express this range.
The other output of Estimate Activity Durations is project documents updates. The
information that may need to be revisited and updated as a result of this process includes
the activity attributes and the assumptions you made regarding resource availability and
skill levels.
Now that you have all the activity information in hand, along with a host of other
inputs, you’re ready to develop the project schedule.
Exam Spotlight
Remember that you perform the Activity processes in this order: Define Activities,
Sequence Activities, Estimate Activity Resources, and Estimate Activity Durations.
Develop Schedule comes after you’ve completed all of these processes.
Desert State University (DSU)
DSU has hired a contract agency to create its new registration website. The website will
allow students in good academic standing to register for classes over the Internet. You
have been appointed as the project manager for the DSU side of this project. You’ll be
working with Henry Lu from Websites International to complete this project.
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Developing the Project Schedule
171
Henry has given you an activity list and asked for time estimates that he can plug into the
project plan.
Your first stop is Mike Walter’s desk. He’s the expert on the mainframe registration
system and he’ll be writing the interface programs to accept registration data from the
new website. Mike will also create the download that the Internet program will use to
verify a student’s academic standing. Mike has created other programs just like this in the
past. His expertise and judgment are very reliable.
The next stop is Kate Langdon. She’s the new team leader of the testing group. Kate has
been with DSU for only one month. Since she has no experience working with DSU data
and staff members, she tells you she’ll get back to you within a week with estimates
for the testing activities. She plans to read through the project binders of some similar
projects and base her estimates against the historical information on similar projects.
She’ll run the estimates by her lead tester before giving them to you.
You’ve asked both of your resources to provide you with three‐point estimates. Mike
Walter’s estimates are an example of using the tool and technique of expert judgment
to derive activity duration estimates. The estimates expected from Kate Langdon will be
derived using historical information (implied by the research she’s going to do into past
similar projects) and expert judgment because she’s involving her lead tester to verify the
estimates.
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Developing the Project Schedule
The Develop Schedule process is the heart of the Planning process group. This is where
you lay out the schedule for your project activities, determine their start and finish dates,
and finalize activity sequences and durations. Develop Schedule, along with Estimate
Activity Resources and Estimate Activity Durations, is repeated several times before you
come up with the project schedule. Most project management software programs today can
automatically build a schedule for you once you’ve entered the needed information for the
activities. The project schedule, once it’s approved, serves as the schedule baseline for the
project that you can track against in later processes.
Remember that you cannot perform Develop Schedule until you have
completed at least the following processes in the Planning group (some
of these can be performed at the same time for smaller, less complex
projects): Collect Requirements, Define Scope, Create WBS, Define
Activities, Sequence Activities, Estimate Activity Resources, Estimate
Activity Durations, and Plan Human Resource Management. In practice,
it’s also beneficial to perform Identify Risks, Perform Qualitative Risk
Analysis, Perform Quantitative Risk Analysis, Plan Risk Responses, and
Plan Procurement Management prior to developing the schedule.
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There is a lot of material to cover in this process, so grab a cup of coffee or a soda now.
I’ll start with the inputs to the Develop Schedule process and then follow up with an in‐
depth discussion of the tools and techniques of the process. These techniques will help you
get to the primary output of this process: the project schedule.
Develop Schedule Inputs
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Develop Schedule has 13 inputs, 9 of which are outputs from other Planning processes. The
inputs are as follows:
■■
Schedule management plan
■■
Activity list
■■
Activity attributes
■■
Project schedule network diagrams
■■
Activity resource requirements
■■
Resource calendars
■■
Activity duration estimates
■■
Project scope statement
■■
Risk register
■■
Project staff assignments
■■
Resource breakdown structure
■■
Enterprise environmental factors
■■
Organizational process assets
You can see how important it is to perform all the Planning processes accurately
because the information you derive from almost every process in the Planning group is
used somewhere else in Planning, many of them here. Your project schedule will reflect
the information you know at this point in time. If you have incorrectly estimated activity
durations or didn’t identify the right dependencies, for example, the inputs to this process
will be distorted and your project schedule will not be correct. It’s definitely worth the
investment of time to correctly plan your project and come up with accurate outputs for
each of the Planning processes.
As with several other processes, you should pay particular attention to constraints and
assumptions when performing Develop Schedule. Constraints are with you throughout
the life of the project. The most important constraints to consider in the Develop Schedule
process are time constraints, and they fall into two categories: imposed dates and key
events/major milestones.
Imposed dates restrict the start or finish date of activities. The two most
common constraints, start no earlier than and finish no later than, are used by most
computerized project management software programs. Let’s look once again at the
house‐painting example. The painting activity cannot start until the primer has dried. If
the primer takes 24 hours to dry and is scheduled to be completed on Wednesday, this
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Developing the Project Schedule
173
implies that the painting activity can start no earlier than Thursday. This is an example
of an imposed date.
Key events or milestones refer to the completion of specific deliverables by a specific
date. Stakeholders, customers, or management staff might request that certain deliverables
be completed or delivered by specific dates. Once you’ve agreed to those dates (even if
the agreement is only verbal), it’s often cast in stone and difficult to change. These dates,
therefore, become constraints.
Be careful of the delivery dates you commit to your stakeholders or
customers. You might think you’re simply discussing the matter or
throwing out ideas, whereas the stakeholder might take what you’ve said
as fact. Once the stakeholder believes the deliverable or activity will be
completed by a specific date, there’s almost no convincing them that the
date needs changing.
Develop Schedule Tools and Techniques
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The primary outputs of Develop Schedule are the schedule baseline and the project
schedule. The schedule baseline is the approved version of the project schedule. You can
employ several tools and techniques to produce these outputs. The tools and techniques
you choose depend on the complexity of the project. For the exam, however, you’ll need to
know them all.
Develop Schedule has eight tools and techniques:
■■
Schedule network analysis
■■
Critical path method
■■
Critical chain method
■■
Resource optimization techniques
■■
Modeling techniques
■■
Leads and lags
■■
Schedule compression
■■
Scheduling tool
A lot of information is packed into some of these tools and techniques, and you should
dedicate study time to each of them for the exam. We’ll look at each one next.
Schedule Network Analysis
Schedule network analysis produces the project schedule. It involves calculating early
and late start dates and early and late finish dates for project activities (as does the
critical path method). It uses a schedule model and other analytical techniques such as
critical path and critical chain method, what‐if analysis, and resource leveling (all of
which are other tools and techniques in this process) to help calculate these dates and
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create the schedule. These calculations are performed without taking resource limitations
into consideration, so the dates you end up with are theoretical. At this point, you’re
attempting to establish the time periods within which the activities can be scheduled.
Resource limitations and other constraints will be taken into consideration when you get
to the outputs of this process.
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Critical Path Method
The critical path method (CPM) is a schedule network analysis technique that estimates
the minimum project duration. It determines the amount of float, or schedule flexibility,
for each of the network paths by calculating the earliest start date, earliest finish date,
latest start date, and latest finish date for each activity (without taking resource availability
into account). This is a schedule network analysis technique that relies on sequential
networks (one activity occurs before the next, a series of activities occurring concurrently
is completed before the next series of activities begins, and so on) and on a single duration
estimate for each activity. The precedence diagramming method (PDM) can be used to
perform CPM. Keep in mind that CPM is a method to determine schedule durations
without regard to resource availability.
The critical path (CP) is generally the longest full path on the project. Any project
activity with a float time that equals 0 or with negative float is considered a critical path
task. The critical path can change under a few conditions. When activities with float time
use up all their float, they can become critical path tasks. Or you might have a milestone
midway through the project with a finish no later than constraint that can change the
critical path if it isn’t met.
Float time is also called slack time, and you’ll see these terms used interchangeably.
There are two types of float: total float and free float. Total float (TF) is the amount of
time you can delay the earliest start of a task without delaying the ending of the project.
Free float (FF) is the amount of time you can delay the start of a task without delaying the
earliest start of a successor task.
In the following section, you’ll calculate the CP for a sample project, and I’ll illustrate
how you derive all the dates, the CP, and the float times.
Gathering Activity and Dependency Information
Let’s say you are the project manager for a new software project. Your team will
be developing a custom application that manages, tracks, and analyzes charitable
contributions to a variety of organizations managed by your parent company. You need to
devise a software system that tracks all the information related to the contributions, the
donors, and the receivers and also supplies the management team with reports that will
help them make good business decisions. For purposes of illustration, I’m showing only a
limited portion of the tasks that you would have on a project like this.
You’ll start this example by plugging information from the processes you’ve already
completed into a table (a complete example is shown later in Table 4.1 in the section
“Calculating the Critical Path”). The list of activities comes from the Define Activities
process. The durations for each activity are listed in the Duration column and were
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Developing the Project Schedule
175
derived during the Estimate Activity Durations process. The duration times are listed
in days.
The Dependency column lists the activities that require a previous activity to finish
before the current activity can start. You’re using only finish‐to‐start relationships. For
example, you’ll see that activity 2 and activity 4 each depend on activity 1 to finish before
they can begin. The dependency information came from the Sequence Activities process.
Now, you’ll proceed to calculating the dates.
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Calculating the Forward and Backward Pass
Project Deliverables is the first activity and, obviously, where the project starts. This
activity begins on April 1. Project Deliverables has a 12‐day duration. So, take April
1 and add 12 days to this to come up with an early finish date of April 12. Watch out,
because you need to count day 1, or April 1, as a full workday. The simplest way to
do this calculation is to take the early start date, add the duration, and subtract 1.
Therefore, the early finish date for the first activity is April 12. By the way, we are
ignoring weekends and holidays for this example. Activity 2 depends on activity 1, so it
cannot start until activity 1 has finished. Its earliest start date is April 13 because activity
1 finished at the end of the previous day. Add the duration to this date minus 1 to come
up with the finish date.
You’ll notice that since activity 4 depends on activity 1 finishing, its earliest start date is
also April 13. Continue to calculate the remaining early start and early finish dates in the
same manner. This calculation is called a forward pass.
To calculate the latest start and latest finish dates, you begin with the last activity.
The latest finish for activity 9 is July 10. Since the duration is only one day, July 10
is also the latest start date. You know that activity 8 must finish before activity 9 can
begin, so activity 8’s latest finish date, July 9, is one day prior to activity 9’s latest start
date, July 10. Subtract the duration of activity 8 (three days) from July 9 and add one
day to get the latest start date of July 7. You’re performing the opposite calculation
that you did for the forward pass. This calculation is called a backward pass, as you
might have guessed. Continue calculating the latest start and latest finish through
activity 4.
Activity 3 adds a new twist. Here’s how it works: Activity 7 cannot begin until activity
3 and activity 6 are completed. No other activity depends on the completion of activity 3.
If activity 7’s latest start date is June 29, activity 3’s latest finish date must be June 28. June
28 minus eight days plus one gives you a latest start date of June 21. Activity 3 depends on
activity 2, so activity 2 must be completed prior to beginning activity 3. Calculate these
dates just as you did for activities 9 through 4.
Activity 1 still remains. Activity 4 cannot start until activity 1 is completed. If
activity 4’s latest start date is April 13, the latest finish date for activity 1 must be April 12.
Subtract the duration of activity 1, and add 1 to come up with a latest start date of April
1. Alternatively, you can calculate the forward pass and backward pass by saying the first
task starts on day 0 and then adding the duration to this. For example, activity number 1’s
earliest start date is April 1, which is day 0. Add 12 days to day 0, and you come up with
an earliest finish date of April 12.
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You determine the calculation for float/slack time by subtracting the earliest start date
from the latest start date. If the float time equals 0, the activity is on the critical path.
Calculating the Critical Path
To determine the CP duration of the project, add the duration of every activity with
zero float. You should come up with 101 days because you’re adding the duration for all
activities except for activity 2 and activity 3. A critical path task is any task that cannot be
changed without impacting the project end date. By definition, these are all tasks with zero
float.
Another way to determine the critical path is by looking at the network diagram. If the
duration is included with the information on the node or if start and end dates are given,
you simply calculate the duration and then add the duration of the longest path in the
diagram to determine the CP. However, this method is not as accurate as what’s shown in
Table 4.1.
Copyright © 2015. John Wiley & Sons, Incorporated. All rights reserved.
Ta b l e 4 .1
CPM calculation
Activity
Number
Activity
Description
Dependency
Duration
Early
Start
Early
Finish
Late
Start
Late
Finish
Float/
Slack
1
Project
Deliverables
—
12
4/1
4/12
4/1
4/12
0
2
Procure
Hardware
1
2
4/13
4/14
6/19
6/20
67
3
Test
Hardware
2
8
4/15
4/22
6/21
6/28
67
4
Procure
Software
Tools
1
10
4/13
4/22
4/13
4/22
0
5
Write Code
4
45
4/23
6/6
4/23
6/6
0
6
Test and
Debug
5
22
6/7
6/28
6/7
6/28
0
7
Install
3, 6
8
6/29
7/6
6/29
7/6
0
8
Training
7
3
7/7
7/9
7/7
7/9
0
9
Acceptance
8
1
7/10
7/10
7/10
7/10
0
Figure 4.3 shows the same project in diagram form. The duration is printed in the top‐right
corner of each node. Add the duration of each path to determine which one is the critical
path.
Remember that CP is usually the path with the longest duration. In Figure 4.1, path
1‐2‐3‐7‐8‐9 equals 34 days. Path 1‐4‐5‐6‐7‐8‐9 equals 101 days; therefore, this path is the
critical path.
Heldman, Kim. PMP: Project Management Professional Exam Study Guide : Updated for the 2015 Exam, John Wiley & Sons, Incorporated, 2015. ProQuest
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Developing the Project Schedule
Figure 4.3
177
Critical path diagram
Act #2
Act #3
2
Hardware
8
Test Hardware
Act #1
12
Deliverables
Act #4
Act #7
Act #8
Act #9
8
Install
3
Training
1
Acceptance
10
Software
Act #5
Act #6
45
Write Code
22
Test & Debug
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Calculating Expected Value Using PERT
Program Evaluation and Review Technique (PERT) is a method that the United States
Navy developed in the 1950s. The Navy was working on one of the most complex
engineering projects in history at the time—the Polaris Missile Program—and needed
a way to manage the project and forecast the project schedule with a high degree of
reliability. PERT was developed to do just that.
PERT and CPM are similar techniques. The difference is that CPM uses the most likely
duration to determine project duration, whereas PERT uses what’s called expected value
(or the weighted average). Expected value is calculated using the three‐point estimates for
activity duration (I talked about three‐point estimates earlier in this chapter) and then
finding the weighted average of those estimates (I’ll talk about weighted average in the next
section, “Calculating Expected Value”). If you take this one step further and determine
the standard deviation of each activity, you can assign a confidence factor to your project
estimates. Without getting too heavily involved in the mathematics of probability,
understand that for data that fits a bell curve—which is what you’re about to calculate with
the PERT technique—the following is true:
■■
Work will finish within plus or minus three standard deviations 99.73 percent of the time.
■■
Work will finish within plus or minus two standard deviations 95.45 percent of the time.
■■
Work will finish within plus or minus one standard deviation 68.27 percent of the time.
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Calculating Expected Value
The three‐point estimates used to calculate expected value are the optimistic estimate,
the pessimistic estimate, and the most likely estimate. Going back to the software
example, let’s find out what these three time estimates might look like for the activity
called Write Code. You get these estimates by asking the lead programmer, or key team
member, to estimate the optimistic, pessimistic, and most likely duration for the activity
based on past experience. Other historical information could be used to determine
these estimates as well. Say in this case that you’re given 38 days for the optimistic
time, 57 days for the pessimistic, and 45 days for the most likely. (Forty‐five days was
derived from the Estimate Activity Durations process and is the estimate you used to
calculate CPM.)
The formula to calculate expected value is as follows:
(optimistic + pessimistic + (4 × mostlikely)) / 6
The expected value for the Write Code activity is as follows:
(38 + 57 + (4 × 45)) / 6 = 45.83
The formula for standard deviation, which helps you determine confidence level, is as
follows:
(pessimistic − optimistic) / 6
The standard deviation for your activity is as follows:
(57 − 38) / 6 = 3.17
You could say the following, given the information you now have:
Copyright © 2015. John Wiley & Sons, Incorporated. All rights reserved.
■■
■■
There is a 68.27 percent chance that the Write Code activity will be completed in
42.66 days to 49 days.
There is a 95.45 percent chance that the Write Code activity will be completed in 39.49
days to 52.17 days.
You calculated the range of dates for the 68.27 percent chance by adding and
subtracting one standard deviation, 3.17, from the expected value, 45.83. You calculated
the 95.45 percent chance by multiplying the standard deviation times 2, which equals 6.34,
and adding and subtracting that result from the expected value to come up with the least
number of days and the most number of days it will take to finish the activity. Generally
speaking, two standard deviations, or 95.45 percent, is a close enough estimate for most
purposes.
Determining Date Ranges for Project Duration
Let’s bring your table of activities back and plug in the expected values and the standard
deviation for each (see Table 4.2).
Heldman, Kim. PMP: Project Management Professional Exam Study Guide : Updated for the 2015 Exam, John Wiley & Sons, Incorporated, 2015. ProQuest
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Developing the Project Schedule
Ta b l e 4 . 2
PERT calculation
Most
Optimistic Pessimistic Likely
Standard
Expected Deviation SD
(SD)
Squared
Value
Activity
Number
Activity
Description
1
Project
10
Deliverables
14
12
12.00
0.67
0.45
2
Procure
Hardware
—
—
—
—
—
—
3
Test
Hardware
—
—
—
—
—
—
4
Procure
Software
Tools
8
14
10
10.33
1.00
1.0
5
Write Code
38
57
45
45.83
3.17
10.05
6
Test and
Debug
20
30
22
23.00
1.67
2.79
7
Install
5
10
8
7.83
0.83
0.69
8
Training
3
3
3
3.00
0
0
9
Acceptance
1
1
1
1.00
0
0
Totals for
CP Tasks
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179
102.99
14.98
The higher the standard deviation is for an activity, the higher the risk.
Because standard deviation measures the difference between the
pessimistic and the optimistic times, a greater spread between the two,
which results in a higher number, indicates a greater risk. Conversely, a
low standard deviation means less risk.
Now let’s look at the total project duration using PERT and the standard deviation to
determine a range of dates for project duration. You should add only the tasks that are on
the critical path. Remember from the CPM example that activities 2 and 3 are not on the
critical path, so their expected value and standard deviation calculations have been left
blank in this table. When you add all the remaining tasks, the total expected value duration
is 102.99 days, or 103 days rounded to the nearest day.
Your next logical conclusion might be to add the Standard Deviation column to get the
standard deviation for the project. Unfortunately, you cannot add the standard deviations
because you will come out with a number that is much too high. Totaling the standard
deviations assumes that all the tasks will run over schedule, and that’s not likely. It is likely
that a few tasks will run over but not every one of them. So now you’re probably wondering
how to calculate the magic number.
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You might have noticed an extra column at the right called SD Squared (or variance).
This is the standard deviation squared—or for those of you with math phobias out there,
the standard deviation multiplied by itself.
Once you have calculated the standard deviation squared for each activity, add the
squares, for a total of 14.98. There’s one more step, and you’re done. Take the square root
of 14.98 (you’ll need a calculator) to come up with 3.87. This is the standard deviation you
will use to determine your range of projected completion dates. Here’s a recap of these last
few calculations:
Total expected value = 103.00
Sum of SD Squared = 14.98
Square root of SD Squared = 3.87
You can now make the following predictions regarding your project:
■■
■■
There is a 68.27 percent chance that the project will be completed in 99.13 days to
106.87 days.
There is a 95.45 percent chance that the project will be completed in 95.26 days to
110.74 days.
Copyright © 2015. John Wiley & Sons, Incorporated. All rights reserved.
Exam Spotlight
For the exam, I recommend that you know that one standard deviation gives you a
68 percent (rounded) probability and two standard deviations give you a 95 percent
(rounded) probability. Also, know how to calculate the range of project duration dates
based on the expected value and standard deviation calculation. You probably don’t need
to memorize how to calculate the standard deviation because most of the questions give
you this information. You should, however, memorize the PERT formula and know how
it works. It wouldn’t hurt to memorize the standard deviation formula as well—you never
know what might show up on the exam.
PERT is not used often today. When it is, it’s used for very large, highly complex
projects. However, PERT is a useful technique to determine project duration when your
activity durations are uncertain. It’s also useful for calculating the duration for individual
tasks in your schedule that might be complex or risky. You might decide to use PERT for a
handful of the activities (those with the highest amount of risk, for example) and use other
techniques to determine duration for the remaining activities.
Critical Chain Method
Critical chain method is a schedule network analysis technique that will modify the
project schedule by accounting for limited or restricted resources, or for unforeseen
project issues, by adding buffers to any schedule path. First construct the project schedule
network diagram using the critical path method. You will apply the duration estimates,
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Developing the Project Schedule
181
dependencies, and constraints and then enter resource availability. Buffers, called feeding
buffers, are added at this time as well. The idea behind feeding buffers is similar to that
of contingencies. Adding buffer activities (which are essentially nonwork activities) to the
schedule gives you a cushion of time that protects the critical path and thus the overall
project schedule from slipping. Feeding buffers are added to noncritical chain‐dependent
tasks that feed into the critical chain. Project buffers are a type of buffer that is added at
the end of the critical chain. According to the PMBOK® Guide, after adding these buffer
activities you should schedule your critical path tasks at their latest start and finish dates.
Once this modified schedule is calculated, you’ll often find that it changes the critical
path. The new critical path showing the resource restrictions and feeding buffers is called
the critical chain.
Critical chain uses both deterministic (step‐by‐step) and probabilistic approaches. A few
steps are involved in the critical chain process:
■■
Construct the schedule network diagram using activity duration estimates (you’ll use
nonconservative estimates in this method).
■■
Define dependencies.
■■
Define constraints.
■■
Calculate critical path.
■■
Enter resource availability into the schedule.
■■
Recalculate for the critical chain.
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The critical chain method typically schedules high‐risk tasks early in the project so that
problems can be identified and addressed right away. It allows for combining several tasks
into one task when one resource is assigned to all the tasks.
Exam Spotlight
CPM manages the total float of schedule network paths, whereas critical chain manages
buffer activity durations. Critical chain is built on CPM and protects the schedule from
slipping.
Resource Optimization Techniques
Earlier, I said that CPM and PERT do not consider resource availability. Now that you
have a schedule of activities and have determined the critical path, it’s time to plug in
resources for those activities and adjust the schedule or resources according to any resource
constraints you discover. Remember that you identified resource estimates during the
Estimate Activity Resources process. Now during Develop Schedule, resources are assigned
to specific activities. Usually, you’ll find that your initial schedule has periods of time with
more activities than you have resources to work on them. You will also find that it isn’t
always possible to assign 100 percent of your team members’ time to tasks. Sometimes your
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182
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schedule will show a team member who is overallocated, meaning they’re assigned to more
work than they can physically perform in the given time period. Other times, they might
not be assigned enough work to keep them busy during the time period. This problem is
easy to fix. You can assign underallocated resources to multiple tasks to keep them busy.
Adjusting the schedule for overallocated resources is a harder problem to fix. We will
look at three techniques that optimize resources to prevent overallocation where possible:
resource leveling, resource smoothing, and reverse resource allocation scheduling. You
should use these techniques with CPM‐based schedules.
Resource Leveling
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Resource leveling—also called the resource‐based method—is used when resources are
overallocated, when they are only available at certain times, or when they are assigned to
more than one activity at a time. In a nutshell, resource leveling attempts to balance out
the resource assignments to get tasks completed without overloading the individual. You
accomplish this by adjusting the start and finish dates of schedule activities based on the
availability of resources. This typically means allocating resources to critical path tasks
first, which often changes the critical path and, in turn, the overall project end date.
The project manager can accomplish resource leveling in a couple of other ways as well.
You might delay the start of a task to match the availability of a key team member, or you
might adjust the resource assignments so that more tasks are given to team members who
are underallocated. Generally speaking, resource leveling of overallocated team members
extends the project end date. If you’re under a date constraint, you’ll have to rework
the schedule after assigning resources to keep the project on track with the committed
completion date. You can accomplish this with resource smoothing, which we’ll look at
next.
Resource Smoothing
Resource smoothing accommodates resource availability by modifying activities within
their float times without changing the critical path or project end date. That means you’ll
also use this technique when you need to meet specific schedule dates and are concerned
about resource availability.
There are several ways you can accomplish this. You can adjust the resource assignments
so that more tasks are given to team members who are underallocated. You could also
require the resources to work mandatory overtime—that one always goes over well!
Perhaps you can split some tasks so that the team member with the pertinent knowledge
or skill performs the critical part of the task and the noncritical part of the task is given
to a less‐skilled team member. Other methods might include moving key resources from
noncritical tasks and assigning them to critical path tasks or adjusting assignments.
Reallocating those team members with slack time to critical path tasks to keep them on
schedule is another option. Don’t forget, fast tracking is another way to keep the project on
schedule.
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Developing the Project Schedule
183
Reverse Resource Allocation Scheduling
Reverse resource allocation scheduling is a technique used when key resources—like
a thermodynamic expert, for example—are required at a specific point in the project
and they are the only resource, or resources, available to perform these activities. This
technique requires the resources to be scheduled in reverse order (that is, from the end date
of the project rather than the beginning) in order to assign this key resource at the correct
time.
Exam Spotlight
Resource leveling can cause the original critical path to change and can delay the
project’s completion date. Resource smoothing modifies activities within their floats
without changing the critical path or project end date. It’s used when changes to the
critical path cannot or should not be made. Reverse resource allocation scheduling is
used when specific resources are needed at certain times.
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Modeling Techniques
Modeling techniques typically include the use of what‐if scenario analysis and simulation.
What‐if scenario analysis uses different sets of activity assumptions to produce multiple
project durations. For example, what would happen if a major deliverable is delayed or
the weather prevents you from completing a deliverable on time? What‐if analysis literally
asks the question, “What if (fill in the blank) happens on the project?” and attempts to
determine the potential positive and/or negative impacts to the project. What‐if questions
help determine the feasibility of the project schedule under adverse conditions. They are
also useful to the project team in preparing risk responses or contingency plans to address
the what‐if situations. Worst‐case what‐if scenarios may result in a no‐go decision.
Simulation techniques use a range of probable activity durations for each activity
(often derived from the three‐point estimates), and those ranges are then used to calculate
a range of probable duration results for the project itself. Monte Carlo is a simulation
technique that runs the possible activity durations and schedule projections many, many
times to come up with the schedule projections and their probability, critical path duration
estimates, and float time.
Exam Spotlight
For the exam, remember that Monte Carlo is a simulation technique that shows the
probability of all the possible project completion dates.
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Leads and Lags
I talked about leads and lags earlier in this chapter. You’ll recall that lags delay successor
activities and require time added either to the start date or to the finish date of the activity
you’re scheduling. Leads require time to be subtracted from the start date or the finish date
of the activity. Keep in mind that as you go about creating your project schedule, you might
need to adjust lead and lag time to come up with a workable schedule.
Schedule Compression
Schedule compression is a form of mathematical analysis that’s used to shorten the project
schedule duration without changing the project scope. Compression is simply shortening
the project schedule to accomplish all the activities sooner than estimated.
Schedule compression might happen when the project end date has been predetermined
or if, after performing the CPM or PERT techniques, you discover that the project is going
to take longer than the original promised date. In the CPM example, you calculated the
end date to be July 10. What if the project was undertaken and a July 2 date was promised?
That’s when you’ll need to employ one or both of the duration compression techniques:
crashing and fast tracking.
Copyright © 2015. John Wiley & Sons, Incorporated. All rights reserved.
Crashing
Crashing is a compression technique that looks at cost and schedule trade‐offs. Crashing
the schedule is accomplished by adding resources—from either inside or outside the
organization—to the critical path tasks. It wouldn’t help you to add resources to noncritical
path tasks; these tasks don’t impact the schedule end date anyway because they have float
time. Crashing could be accomplished by requiring mandatory overtime for critical path
tasks or requiring overnight deliveries of materials rather than relying on standard shipping
times. You may find that crashing the schedule can lead to increased risk or increased costs
or both.
Be certain to check the critical path when you’ve used the crashing
technique because crashing might have changed the critical path. Also
consider that crashing doesn’t always come up with a reasonable result. It
often increases the costs of the project as well. The idea with crashing is
to try to gain the greatest amount of schedule compression with the least
amount of cost.
Fast Tracking
I talked about fast tracking in Chapter 1, “What Is a Project?” Fast tracking is performing
two tasks or project phases in parallel that were previously scheduled to start sequentially.
Fast tracking can occur for the entire duration of the task or phase or for a portion of the
task or phase duration. It can increase project risk and might cause the project team to
have to rework tasks. Fast tracking will work only for activities that can be overlapped. For
example, it is often performed in object‐oriented programming. The programmers might
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Developing the Project Schedule
185
begin writing code on several modules at once, out of sequential order and prior to the
completion of the design phase. However, if you remember our house‐painting example,
you couldn’t start priming and painting at the same time, so fast tracking isn’t a possibility
for those activities.
Copyright © 2015. John Wiley & Sons, Incorporated. All rights reserved.
Scheduling Tool
Given the examples you’ve worked through on Develop Schedule and resource leveling,
you have probably already concluded how much a scheduling tool might help you with
these processes. The scheduling tools I’ve used are in the form of project management
software programs. They will automate the mathematical calculations (such as forward
and backward pass) and perform resource‐leveling functions for you. Obviously, you can
then print the schedule that has been produced for final approval and ongoing updates. It’s
common practice to email updated schedules with project notes so that stakeholders know
what activities are completed and which ones remain to be done.
It’s beyond the scope of this book to go into all the various software programs available
to project managers. Suffice it to say that scheduling tools and project management
software range from the simple to the complex. The level of sophistication and the types of
project management techniques that you’re involved with will determine which software
product you should choose. Many project managers that I know have had great success
with Microsoft Project software and use it exclusively. It contain…
