CST 650 University of Management and Technology CST 650 Agile and Iterative Project Management

CST 650. Agile and Iterative Project Management

Assignment 2

1.Michelle Grancesos is the visionary CEO of Appliance Masters Toaster Co. While taking a shower, she has a breakthrough insight into a new concept of toaster that Appliance Masters should be developing. In Michelle’s view, the toaster can take advantage of new information technology and become the brains of the kitchen. Following are some features she envisions in the New Age Toaster:

? Voice recognition, so that it can understand spoken instructions

? Voice synthesizer, so that it can speak to user

? Toasts bread

? Oven toasting capabilities to cook small items (e.g., hot dogs)

? Command center, so that it controls all kitchen appliances – the oven, the dishwasher, the range, the garbage disposal, vents, and lights.

Using the Poor Man’s Hierarchy, prioritize the features that Michelle proposes to include in her New Age Toaster.

2. In brainstorming features of a “new age” toaster at Appliance Masters, the five following features stood out. As a consequence of a market survey of 20 panelists, market researchers were able to develop “value scores” for each of the features. These are shown in parentheses and they add up to 1.00.

Voice recognition, so that it can understand spoken instructions (0.10)

Voice synthesizer, so that it can speak to user (0.15)

Toasts bread (0.50)

Oven toasting capabilities to cook small items (e.g., hot dogs) (0.20)

Command center, so that it controls all kitchen appliances – the oven, the dishwasher, the range, the garbage disposal, vents, and lights (0.05).

Create a Pareto diagram that reflects potential customer preferences for features. Which features should be contained in early versions of the toaster?

3. A big challenge facing iterative projects is to estimate what work efforts should be undertaken in individual iterations. One approach to estimating work efforts per iteration is to start by creating a rough PERT/CPM chart that lays out your best understanding of what needs to be done on the project. It is important that the PERT/CPM chart show both tasks and resulting milestones, where milestones reflect executable code.

The PERT/CPM chart below shows task sequences and durations associated with a hypothetical project.Using the information contained in the PERT/CPM chart:

a) Calculate the critical path;

b) Calculate latest and earliest start dates for each task and milestone;

c) Calculate float for each task.

Assuming the target length of an iteration is about 4 weeks (20 days if you ignore weekends), identify how you would organize the tasks by iteration. Assume you have all the resources you need. Explain how working with known resource constraints would affect how you carry out this exercise.

1. 4. Exercise: Catching the 7:00 am Metroliner Train to New York

In order to make her 10:30 am client meeting in New York City, Marsha needs to catch the 7:00 am Metroliner train at Union Station in Washington, DC.When she arrives at the Union Station parking lot, it is 6:40 am, so she has 20 minutes before her train leaves.The trip from the parking lot to the ticket counter typically takes three minutes.Following is a list of things she hopes to do:

• Purchase tickets (min: 3 minutes, max: 8 minutes if there is a long line)

• Buy coffee and donuts (min: 1 minute, max: 4 minutes if there is a long line)

• Consume coffee and donuts at food court table (min: 4 minutes, max: 6 minutes) (The alternative is to consume the coffee and donuts on the train.)

• Buy newspaper (min: 1 min, max: 2 minutes)

• Board train at 6:50 am to be assured of locating a good seat

• Browse through bookstore, where there is currently a fantastic sale on best sellers

Question:How should Marsha schedule her time?

Tutorial on Project Scheduling
with PERT/CPM
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Tutorial on PERT/CPM
Background
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Tutorial on PERT/CPM
Introduction
The best known planning tool in the project manager’s tool box is
the PERT/CPM network diagram. This tutorial is designed to provide
scheduling novices with a more detailed treatment of developing
PERT/CPM charts than what is contained in the basic planning
module.
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Tutorial on PERT/CPM
What Is PERT/CPM?
PERT was developed by the US Navy in 1957. It is an acronym that
stands for Project Evaluation and Review Technique. It is a systems
diagram that shows how project tasks should be sequenced.
CPM was developed by DuPont Corporation in 1958. Conceptually,
it is quite similar to PERT networks. Like PERT, it shows how
project tasks should be sequenced.
What we call PERT/CPM in this course has taken on the name
precedence diagrams. Precedence diagrams are a hybrid of the
PERT and CPM approaches. Use of precedence diagrams to
schedule projects is called the precedence diagram method (PDM).
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Tasks
Tasks represent work effort of some sort. Examples of tasks include:
Testing a piece of software code (working time task)
Laying brick (working time task)
Paint drying (elapsed time task)
Note that the first two examples of tasks entail the application of
people to carry out the work. If the people stop work (e.g., during
lunch break, over weekends), the work does not get done. This type
of task is called a working time task
Note that in the third example, work is carried out passively. There is
no application of physical effort by workers. This type of task is
called an elapsed time task. It operates according to a 24/7
schedule – paint will dry 24 hours a day, seven days a week.
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Milestones
Milestones are markers. Unlike tasks, they don’t reflect active or
passive work effort.
Milestones are usually set up to establish targets toward which we
can direct work efforts. For example, “Design Phase Is Finished, 15
October” may be a milestone indicating that a series of designrelated tasks should be completed by 15 October.
Milestones are good for tracking work. As a project is carried out,
project staff can check off the milestones they have achieved and
report these accomplishments to senior managers.
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Representing Tasks and Milestones
on a PERT/CPM Chart
Tasks
Start
Dig hole
Pour
concrete
Milestone Markers
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Concrete
cure
Excavation
phase ended
PERT/CPM Charts Are Systems Diagrams
The development of PERT/CPM network charts was a consequence
of advances in systems engineering in the 1950s. The use of flow
charts became big at this time. Flow charts are diagrams that clearly
illustrate processes.
In the 1950s, engineers began asking how flow chart concepts could
be applied to scheduling projects. Ultimately, this quest led to the
development of PERT and CPM
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Traditional Flowchart: Picnic Project
Check weather
Note that in this flow chart,
the rectangular boxes
represent processes (e.g.,
“Prepare indoor activities”) and
the diamond represents a
decision that needs to be made
(e.g., “Rain?”; if “Yes,” proceed
down one path; if “No,”
proceed down the other path).
The terminator (i.e., “Hold
picnic”) represents the end of
the decision sequence. When
properly constructed, flow
charts like the one portrayed
here give system developers
the precise information they
need to build solutions that
meet the specifications.
Yes
Rain?
No
Prepare indoor
activities
Prepare outdoor
activities
Caterer sets
up indoors
Caterer sets
up outdoors
Hold picnic
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Basic PERT/CPM Network Logic
Good practice requires that
all PERT/CPM charts start
with a “Start” milestone
Start
Plan
picnic
“Get food” and “Get
sports equipment” are
carried out in parallel
Good practice requires that
all PERT/CPM charts end
with an “End” milestone
Get food
Drive to
site
Get
sports
equip
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Hold
picnic
End
Differences between
Flow Charts and PERT/CPM Charts
Flow charts have conditional logic, e.g., “If it is raining, then do X. If
it is not raining, then do Y.” PERT/CPM charts do not have
conditional logic. The chart does not incorporate decision making.
Flow charts allow you to go back to an earlier activity, e.g., “If fewer
than 20 orders have been filled, then go back to step 3 and repeat
the process.” PERT/CPM charts do not go back to earlier tasks.
They move inexorably forward in time. If a given set of steps need to
be repeated, these steps are laid out all over again in the chart.
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Critical Path Concept
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Identifying the Critical Path
Wire
house
Start
Lay
foundation
14 days
Frame house
20 days
2 days
Put up
dry wall
Install
plumbing
4 days
End
3 days
Note that there are two paths in this PERT/CPM chart
Upper path: Foundation → Frame → Wire → Dry wall
Duration: 40 days
Lower path: Foundation → Frame → Plumbing → Dry wall
Duration: 41 days
The path indicated by thick red arrows is called the critical path. It is the
longest path in the network. As such, it defines the length of the project.
In this case, the project is scheduled to last 41 days.
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Task Durations May Depend
on Number of Resources Used (1)
In the previous example of a PERT/CPM chart, the duration of
“Frame house” was listed as 20 days. Let’s say this duration is
based on using 4 carpenters to do the job. The overall level of effort
to do the job is defined as:
LOE = duration x number of resources
LOE = 20 days x 4 carpenters = 80 carpenter-days
Level of effort is useful in computing task duration when we know
how many resources can be applied to the task. For example, if we
have only two carpenters available to frame the house
Duration = 80 carpenter-days/2 carpenters = 40 days
If we have eight carpenters,
Duration = 80 carpenter-days/8 carpenters = 10 days
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Task Durations May Depend
on Number of Resources Used (2)
In working with level of effort data, the trick, of course, is
computing what the value is. The best way to compute level of
effort is to follow the approach taken here. Let’s say that we
usually work with teams of four carpenters, and that we find on a
typical house building project it takes them 20 days to frame the
house. Consequently, this one example tells us that the level of
effort for framing a house is 80 carpenter-days of effort.
In working with level of effort, you need to employ good sense.
While saying that the house can be framed in twenty days with
four carpenters or forty days with two carpenters sounds
reasonable, it is silly to extend this logic to its extreme and to say
that 160 carpenters can do the job in one day!
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Importance of the Critical Path
The critical path is called critical because it defines the length of the project.
Any delays along the critical path can translate into delays in the project
overall. For example, if it takes 5 days to install the plumbing instead of the
scheduled 3 days, this can result in a two day schedule slippage.
Note that the “Wire house” task is non-critical. The network shows that it is
scheduled to take 2 days, while the parallel plumbing task (which is a critical
path task) is scheduled to take 3 days. Consequently, “Wire house” has one
day of float (also called slack by some schedulers). You can have a one day
delay on this non-critical task without causing the project to slip its schedule.
On large projects, you do not need to monitor progress on every path. The
important thing is to monitor progress on the critical path.
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Earliest Start, Latest Start, Float (Slack)
Task A
Task B
3 days
5 days
Start
Task C
Task D
8 days
2 days
Task E
5 days
End
The critical path is the longest path. Add up the durations on different
paths, and identify the longest path. In this case, the longest path is
pictured in red. Its duration is 15 days. This means the project duration
is scheduled to be 15 days.
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Calculating Earliest Start
ES = Day 0
ES = Day 3
Task A
Task B
3 days
5 days
Start
Task E
Task C
Task D
5 days
8 days
2 days
ES = Day 10
ES = Day 0
ES = Day 8
End
To calculate the earliest time a task can begin, start at the left of the chart and work your way to
the right. Add the duration of a newly encountered task to the total up to that point.
Begin computing earliest start dates with the critical path. In the network above, the earliest Task C
can begin is at time t = 0. If C takes 8 days to complete, the earliest Task D can begin is at time t =
8. If D takes 2 days to complete, then the earliest Task E can begin is at time t = 10.
On the top, non-critical path above, the earliest Task A can begin is at time t=0. If it takes 3 days to
complete, then earliest Task B can begin is at t = 3. Note that we have already determined by our
critical path computation that Task E begins at time t = 10.
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Calculating Latest Start
LS = 2 days
LS = Day 5
Task A
Task B
3 days
5 days
Start
Task E
Task C
Task D
5 days
8 days
2 days
LS = Day 10
LS = Day 0
LS = Day 8
End
To calculate the latest time a task can begin, start at the right side of the chart and work your way to the subtracting
durations, task by task.
Note that calculating latest task dates for the critical path is easy, because on the critical path earliest starts and latest
starts are the same (ES = LS) – there is no leeway.
On the top, non-critical path above, the latest Task E can begin is 5 days before the project end. Since the project will
last 15 days, LS for Task E is 10. The latest start for Task B is 5 days before the latest start of Task E, or 10 – 5, so LS
= 5. Finally, the latest start for Task A is 3 days before the latest start of Task B, or 5-3, so LS = 2.
Note that the latest start is sometimes called the “drop dead” date. If you begin later than the latest start date,
then you can cause the project to encounter schedule slippage. For example, in the network diagram provided
here, If Task B begins on Day 7 (two days later than Task B’s latest start date), this can cause a two day delay in
the project overall. What was initially a non-critical path has now become critical.
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Calculating Float (Also Called Slack)
ES = Day 0
ES = Day 3
LS = Day 2
LS = Day 5
Float = 2
Float = 2
Task A
Task B
3 days
5 days
Start
Float = LS – LE
Task E
Task C
Task D
5 days
8 days
2 days
ES = Day 10
ES = Day 0
ES = Day 8
LS = Day 10
LS = Day 0
LS = Day 8
Float = 0
Float = 0
Float = 0
End
Float measures scheduling leeway
for a task. Note that critical path
tasks have zero float – there is no
leeway!
In a sense, float is a measure of forgiveness. For example, Task A has 2 days of float associated with it. I can begin
Task A a day late, and this will not affect the project schedule. However, if I begin it three days late, this can
contribute to a slip of the overall schedule.
Critical path tasks are unforgiving. This is indicated by the fact that each of them has zero float. If you begin a
critical path task even a little late, this translates into overall schedule slippage. The idea that there is no
forgiveness on the critical path is a common sense one. Remember, the critical path defines project length. So if
there is even a small delay on any of the critical path tasks, this can extend the project schedule.
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Hard Logic and Soft Logic
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Not All Precedence Links Are Equal
Non-critical path
Hard logic link: Pour coffee
must follow Fix coffee
Start
Fix Coffee
Pour Coffee
8 minutes
2 minutes
Fix Cereal
Make Toast
6 minutes
6 minutes
Duration = 10 min
Float = 2 min
End
Critical path
Duration = 12 min
Soft logic link: It doesn’t
matter which of these two
tasks is predecessor and
which is successor
With hard logic links, tasks must occur in a prescribed sequence. These links cannot be
broken. With soft logic links, the sequence is immaterial. These links can be broken.
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Soft Logic Links Can Be Broken
Start
Fix Coffee
Pour Coffee
8 minutes
2 minutes
End
Fix Cereal
6 minutes
Make Toast
6 minutes
By breaking the soft logic link between “Fix Cereal” and “Make Toast,” I am
able to reconfigure the network diagram to have these two tasks carried out
in parallel. This has the effect of shortening the project duration, because
the new critical path is the top path – it has a 10 minute duration. Two
minutes have been shaved off duration! (See previous chart.)
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Estimating Task Duration
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Estimating Task Durations with PERT/CPM
When PERT networks were first developed in the late 1950s, one of
their distinguishing features was the way they estimated task
duration. To compute the expected time [e(t)] of a task, they
employed the following formula:
e(t) = a + 4b + c , [where a = best case, b = typical case, and
6
c = worst case]
Example:
e(t) = 40 + 4×43 + 47 , [where a = 40 hrs, b= 44 hrs, c = 47 hrs]
6
= 44.33 hours
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Estimating Standard Deviation for Task Durations
Standard deviation is an indicator of the “slop” of a measure. A
measure that is right on target has a low standard deviation. The
rougher the measure, the greater its standard deviation.
The inventors of PERT developed a simple formula that provides an
approximation of the standard deviation (SD) associated with the
estimate of the expected duration of a task:
SD(t) = c – a , where c = worst case, a = best case
6
Example: If c = 47 hrs and a = 43 hrs, SD(t) = 0.67 hrs
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Using Expected Duration with Its
Standard Deviation (1)
In the previous examples, we have
e(t) = 44.33 and SD(t) = 0.67
Combining the two pieces of information we report that:
e(t) = 44.33 +/- 0.67 hours
That is, we have reason to believe that the true amount of time it will
take to carry out the target task lies somewhere between 43.67
hours and 45.00 hours. We know from our understanding of the
normal distribution that about 68% of observations lie within +/- 1
standard deviation from the mean. Very roughly, we have a sense
that two-thirds of the time, the amount of time it will take to carry out
our task lies within the range of 43.67 and 45.00 hours.
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Using Expected Duration with Its
Standard Deviation (2)
Note, that we have to be very careful when talking about assuming that deductions arising from
the normal distribution apply to the Beta distribution (the (a + 4b +c)/6 formula we are using here
provides an estimate of the mean of the Beta distribution). Clearly, the normal distribution is
symmetric about the mean, while the Beta distribution is skewed. Still, it turns out that about twothirds of the observations on a typically encountered Beta distribution (such as presented in this
example) lie within a range slightly larger than +/- 1 standard deviation from the mean, so the 1
standard deviation rule for normal distributions roughly applies to the Beta distribution. However,
the 2 standard deviation scenarios differ significantly between the normal and Beta distributions.
For the normal distribution, roughly 95 percent of the observations lie within +/- 2 standard
deviations from the mean. However, with the Beta distribution 95% of the observations lie in the
following range: μ – 1.5 x (c – a)/6 and μ + 1.95 x (c – a)/6, where μ is a measure of the mean.
Thus in the present case, we estimate that 95% of the time, the actual amount of time it will take
to carry out the task being examined lies in the range 43.3 hours and 45.6 hours.
For a typical Beta distribution – as reflected in the data presented in this example – about 70% of
the observations lie at 0.82.
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Estimating the Duration of the Critical Path (1)
To estimate the duration of the critical path, merely add up the
duration of the individual tasks that lie on the critical path.
To estimate the standard deviation of the critical path, carry out the
following computation:
SDPath = SQRT(SD12 + SD22 + SD32 + … + SDi2) for i tasks on the
path.
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Estimating the Duration of the Critical Path (2)
Note: The units of analysis in this table are hours.
Task
A
B
C
D
E
Best case
3
12
6
10
2
Most typical Worst case
4
15
8
13
4
7
18
12
18
6
Duration =
Expected
duration
Standard
deviation
4.33
0.67
15.00
1.00
8.33
1.00
13.33
1.33
4.00
0.67
45.00 SD Sqrd =
SD =
Duration of path = 45 hours +/- 2.16 hours
SD Squared
0.44
1.00
1.00
1.78
0.44
4.67
2.16
In this example, Tasks A, B, C, D, and E comprise the critical path. For each task, we compute expected duration
based on our assessment of the best case, most typical case, and worst case (using the Beta distribution). By
adding up these numbers, we get the expected duration of the critical path (45). Given this data, we are also able
to estimate the standard deviation associated with the duration of each task. By squaring these values and
summing them, we get the sum of 4.67 (which in statistics is called variance). Standard deviation is the square root
of variance, so in this example it is 2.16. Thus we estimate that the critical path will consume 45 hours of effort,
plus or minus 2.16 hours. As a rough rule of thumb, about two-thirds of our observations lie within one standard
deviation from the mean, so we are saying that there is a about a 30-35% chance of the true value lying outside
the specified range.
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The Need to Estimate a Range of Duration Times
Up until now, all of our estimates of task duration have been point
estimates. That is, we use a single value of duration. In reality, we
know that these estimates are likely to be wrong. When we say it
takes 1.2 days to test a software algorithm, we don’t seriously
expect it to take exactly 1.2 days. We figure it will take 1.2 days, plus
or minus some segment of time.
In statistics, the “plus or minus” factor is determined by a measure
called standard deviation (SD). By calculating SD for a task, you
have a better idea of how much faster or slower the task will be than
what you speculate with your point estimate.
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Practical Steps in Building a PERT/CPM Chart
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Step 1. Draw a Logic Diagram by Hand
Sometimes you see project workers trying to develop a PERT/CPM
chart by working directly with a scheduling software package.
Generally, this is an ineffective way to begin. The computer screen
is limited in size and only lets you see a handful of tasks at one time.
Seasoned professionals always begin by drawing the logic relations
of tasks by hand on large sheets of paper or on large white boards
mounted onto a wall. This way they can work with big chunks of the
project and perhaps even see the whole project at one time.
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Step 2. Build a PERT/CPM Chart
Based on Your Hand Drawn Chart
If you are using computer software, now is the time to build a
PERT/CPM network on the computer, using the large hand drawn
chart as your guide. As you build the chart, enter task duration data.
If you are building a PERT/CPM network by hand, copy your large
rough chart, and enter task duration figures into each box that
represents a task.
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Step 3. Identify the Critical Path
On a computerized scheduling package, once the scheduling data
are entered into the system, the critical path will be identified
automatically. It is usually pictured as a red path.,
If you have created a PERT/CPM network manually, look at all the
paths that run through the network and find the one that is longest.
This is the critical path. Color it red.
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Dealing with Weekends, Holidays, and Such
Computerized scheduling packages can deal with weekends,
holidays, and such automatically. Each of these packages contains
a central calendar, where you can define what days are weekend
days (in Muslim countries, you set weekends for Friday and
Saturday), what days are holidays (e.g., you can set New Years Day
as a holiday). Beyond this, with computerized scheduling packages
you can identify elapsed time activities (e.g., paint drying, concrete
curing), so that these activities are carried out according to a 24/7
calendar. That is, if you set “Paint dry” as an elapsed time activity,
the software will schedule it to dry on weekends (when appropriate)
as well as weekdays.
When you create PERT/CPM networks by hand, you need to track
weekends, holidays, and elapsed time tasks manually.
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