28. The following are body mass index (BMI) scores measured in 12 patients who are free of diabetes
and are participating in a study of risk factors for obesity. Body mass index is measured as the ratio of
weight in kilograms to height in meters squared. Generate a 95% confidence interval estimate of the true
BMI.
25
27
31
33
26
28
38
41
24
32
35
40
Upper limit of CI: 27.929
Lower limit of CI: 35.404
29. How many subjects would be needed to ensure that a 95% confidence interval estimate of BMI had a
margin of error not exceeding 2 units?
25
27
31
33
26
28
38
41
24
32
35
40
42
30. Based on the data set below , what is the standard deviation?
25
27
31
33
26
28
38
41
24
32
35
40
5.88

31. Peak expiratory flow (PEF) is a measure of a patient’s ability to expel air from the lungs. Patients with
asthma or other respiratory conditions often have restricted PEF. The mean PEF for children free of
asthma is 306. An investigator wants to test whether children with chronic bronchitis have restricted PEF.
A sample of 40 children with chronic bronchitis is studied, and their mean PEF is 279 with a standard
deviation of 71. Is there statistical evidence of a lower mean PEF in children with chronic bronchitis? Run
the appropriate test at
= 0.05.

32. Peak expiratory flow (PEF) is a measure of a patient’s ability to expel air from the lungs. Patients with
asthma or other respiratory conditions often have restricted PEF. The mean PEF for children free of
asthma is 306. An investigator conducts a study to investigate whether there is a difference in mean PEF
in children with chronic bronchitis as compared to those without asthma or other respiratory conditions
often have restricted PEF. Data on PEF are collected and summarized below. Based on the data, is there
statistical evidence of a lower mean PEF in children with chronic bronchitis as compared to those
without? Run the appropriate test at
= 0.05.

33. A clinical trial is run to investigate the effectiveness of an experimental drug in reducing preterm
delivery to a drug considered standard care and to a placebo. Pregnant women are enrolled and
randomly assigned to receive either the experimental drug, the standard drug or a placebo. Women are
followed through delivery and classified as delivering preterm (< 37 weeks) or not. The data are shown
below.
Preterm Delivery
Experimental Drug
Standard Drug
Placebo
Yes
17
23
35
No
83
77
65
Is there a statistically significant difference in the proportions of women delivering preterm among the
three treatment groups? Run the test at a 5% level of significance.