biostatistics

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HP302 Homework Assignment 1, Due Wednesday, January 31st by 11:59 pm

Answer the following questions and submit your answers via Blackboard by the due date. There are a

total of 34 possible points.

1. Complete the following equation using the order of operations. (2 pts)

25 ∗ 2 −
62

(16 + 2)
− 4

a. 0.78

b. 48

c. 44

d. 0

2. Complete the following equation using the order of operations. (2 pts)

((9 + 7) − 5) × 22 −
48

2

a. 44

b. 40

c. 20

d. 5

A study from Baltimore, Maryland wants to study the differences in initiation of tobacco use between

adolescents that started working for pay and adolescent that did not work. 150 high school students

were followed in each group and it was recorded whether or not they started tobacco use.

3. True or False: The “exposure” is whether or not adolescents worked for pay. (2 pts)

4. True or False: The “disease” (i.e. outcome) is known at the beginning of the study. (2 pts)

5. What kind of study is being conducted? (2 pts)

a. Case-Control

b. Cross-Sectional

c. Prospective Cohort

d. RCT

A doctor wants to research the effects of smoking while pregnant on the birthweight of the

newborn, i.e. does smoking while pregnant lead to abnormally small birthweights. The

birthweight of 508 hundred newborns were first identified as having a normal or abnormal

birthweight. The new mothers were then interviewed about their tobacco usage while

pregnant. Below are the results.

Maruf Tirkestani

Maruf Tirkestani

Maruf Tirkestani

Maruf Tirkestani

Maruf Tirkestani

2

Abnormal Birthweight Normal Birthweight Total
Mother smoked at least once a week 52 34 86
Mother did not smoke at all 71 251 322
Total 123 285 508

6. What kind of study design is this? (2 pts)
a. Case-Control
b. Case Report
c. Cross-Sectional
d. RCT
7. True or False: The “exposure” is the birthweight. (2 pts)
8. Using the data from questions 6 – 7, what is the odds ratio of a women giving birth to a child
with abnormally small birthweight if she smoked at least once a week during pregnancy
compared to if she didn’t smoke at all during pregnancy? (Round to 2 decimal places.) (3 pts)
a. 2.72
b. 5.40
c. 3.51
d. 0.37

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A small cohort study consisting of 10 women over the age of 50 with low bone density were followed for
10 months. Below are the clinical outcomes per patient per month.
In
d
iv
id
u
a
l
1

2

Lost to follow-up

3

Death

4

Osteoporotic Fracture

5

Death

6

Lost to follow-up

7

8
Osteoporotic
Fracture
9

Osteoporotic Fracture

10

Osteoporotic Fracture

0 1 2 3 4 5 6 7 8 9 10

Months

9. What is the prevalence of osteoporotic fractures at 7 months assuming once a woman develops
a fracture, she continues to have it for the remainder of the study period? (Round to 2 decimal
points.) (2 pts)
a. 0.1
b. 0.2
c. 0.3
d. 0.4
10. What is the cumulative incidence at 10 months? (Round to 2 decimal points.) (2 pts)
a. 0.2
b. 0.4
c. 0.6
d. 0.8

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11. What is the incidence rate of developing an osteoporotic fracture in 10 months per 10,000
person-months? (3 pts)
a. 571
b. 500
c. 714
d. 936

A study looking at the relationship between tanning and cancer invited 100 participants to report on
their tanning and melanoma history. Below are the results.
Melanoma No Melanoma Total
Tanned at least twice a week 37 18 55
Doesn’t tan at all 20 25 45
Total 57 43 100

12. What is the prevalence of melanoma in those who have had no history of tanning? (Round to 2
decimal points.) (2 pts)
a. 0.44
b. 0.45
c. 0.57
d. 0.20
13. What is the prevalence of melanoma in those who had a history of tanning at least twice a
week? (Round to 2 decimal points.) (2 pts)
a. 0.57
b. 0.67
c. 0.55
d. 0.37
14. What is the relative risk of melanoma in those who tanned at least twice a week versus those
with no history of tanning? (3 pts)
a. 2.57
b. 3.63
c. 1.52
d. 0.55
15. What percent of melanoma cases could potentially be preventable if the participants no longer
tanned at least twice a week (i.e. what is the PAR?)? (Round to 2 decimal places.) (3 pts)
a. 0.44
b. 0.57
c. 0.23
d. 0.77