Short answers:1. A researcher meets with a biostatistician to go over their analysis plan for an observational study.
The biostatistician states, “Although you are primarily interested in the relationship between
exposure to second-hand smoke (SHS) and birth weight, a simple comparison of the birth weights
for the SHS groups is not appropriate. However, ANCOVA can be used to help answer your research
question.” Explain the biostatistician’s statement.
2. A 2-year study was conducted to investigate bicycle safety at a city’s 10 most congested
intersections. The primary variable of interest was the number of accidents that involved a bicycle.
What descriptive measures and graphs can you use to describe the number of accidents involving
a bicycle as:
a.
b.
a continuous variable (actual number of accidents)?
an ordinal variable (few accidents, some accidents, many accidents)?
3. A researcher wanted to examine the effects of a new potassium supplement on blood pressure.
They ask you to develop their study design.
a.
How would you design a study to examine whether this new potassium
supplement can decrease blood pressure for adults in the United States? Why?
b.
How would you better design the study to exclude the influence of age,
gender and race? Why?
c.
How would you study the relationship between potassium intake and blood
pressure in the general population if experiments were not viable? Explain your
rationale.
4. A researcher wanted to test if triglyceride levels, an important marker for risk of coronary artery
disease, differed between men and women. The results of their study analysis are attached below.
a.
What is the null hypothesis (in words) and what type of test is this?
b.
Are the variances equal for the distribution of triglyceride levels in men and
women (remember to provide value for test statistic and P-value)?
c.
Are the mean triglyceride levels significantly different in men versus women
(remember to provide value for test statistic and P-value). If yes, which group has a
significantly higher level?
Variable: triglyceride (triglyceride)
Sex
N
Mean
Std Dev
Std Err
Minimum
Maximu
m
Female
53
173.8
14.8
2.0
151.0
200.0
Male
47
249.6
77.8
11.4
147.0
450.0
-75.8
54.4
10.9
Difference
(female-male)
Test Equality of Variances
Method
Num DF
Den DF
F Value
P-value
Folded F
46
52
27.73
