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Question 1
The following data were collected in a clinical trial to compare a new drug to a placebo for its
effectiveness in a lowering total serum cholesterol. Generate a 95% confidence interval for the
difference in mean total cholesterol levels between treatments.
New Drug (n=75) Placebo (n=75) Total sample (n=150)
Men (SD) Total
Serum Cholesterol
185.0 (24.5) 204.3 (21.8) 194.7 (23.2)
% patients with Total
Cholesterol < 200
78.0% 65.0% 71.5%
A. Upper limit -11.88
B. Lower limit -26.72
C. Based on the confidence interval which of the following is (are) true? (a) There is significant
evidence, alpha = 0.05, to show that there is a difference in total serum cholesterol between
treatments New Drug and Placebo (b) There is not significant evidence, alpha = 0.05, to show
that there is a difference in total serum cholesterol between treatments New Drug and Placebo (c)
The difference between total cholesterol between treatments New Drug and Placebo is
essentially 0 (d) b and c.
Question 2
A study is designed to investigate whether there is a difference in response to various treatments
in patients with rheumatoid arthritis. The outcome is patient’s self-reported effect of treatment.
The dada are shown below. Are symptoms independent of treatment? Conduct a ChiSquare test
at a 5% level of significance.
Symptoms
Worsened
No Effect Symptoms
Improved
Total
Treatment 1 22 14 14 50
Treatment 2 14 15 21 50
Treatment 3 9 12 29 50
A. df 4
B. critical value 9.4877
C. computed statistics 11.3560
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Based on comparing the computed statistics to the critical value which of the following is (are)
true? (a) There is significant evidence, alpha = 0.05, to show that treatment and response are not
independent (b) there is not significant evidence, alpha = 0.05, to show that treatment and
response are not independent (c) there is significant evidence, alpha = 0.05, to show that
treatment and response are independent (d) b and c
Question 3
An investigator conducts a study to investigate whether there is a difference in means PEF in
children with chronic bronchitis as compared to those without. 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? Apply the two sample t test at
alpha = 0.05.
Group Number of children Mean PEF Std Dev PEF
Chronic Bronchitis 25 281 68
No chronic bronchitis 25 319 74
1. z 95% confidence interval = 1.96
2. Upper limit 95% CI = 349.55
3. Lower limit CI 95% = 288.45
4. Based on comparing the critical the upper and lower limits of the confidence interval for the
mean of PEF for children with no Chronic Bronchitis to the mean PEF for children with
bronchitis which of the following is (are) true? (a) There is statistical evidence of a lower mean
PEF in children with chronic bronchitis as compared to those without (b) There is NOT statistical
evidence of a lower mean PEF in children with chronic bronchitis as compared to those without
(c) The confidence interval contains the mean PEF for the No chronic bronchitis group (d) a and
c
Question 4
The following are body mass index (BMI) scores measured in 12 patients who are free of diabetes and
particularly 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 = 35.40
Lower limit of CI = 27.93
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8. Which of the following is true?
a. if a 90% CI for the mean is (75.3 to 80.9), we would reject HO: Mean=70 in favor of H1; Mean ≠70 at
alpha= 0.05 (b) If a test is run and p=0.0356, then we can reject HO at alpha = 0.01 (c) If a 95% CI for the
difference in two independent means is (-4.5 to 2.1), then the point estimate is -2.1 (d) If a 95% CI for the
difference in two independent mean is (2.1 to 4.5), there is no significant difference in means (e) The
margin of error is always greater than or equal to the standard error
Question 5
A randomized controlled trial is run to evaluate the effectiveness of a new drug for asthma in children. A
total of 250 children are randomized to either the new drug or placebo (125 per group). There are 63
boys assigned to the new drug group and 58 assigned to the placebo. Is there a statistically significant
difference in the proportion of the boys assigned to the treatments? Apply the appropriate test at a 5%
level of significance (1) Critical value = +/- 1.96 (2) computed statistics 0.63(3) Based on comparing the
computed statistics to the critical value which of the following is (are) true? (a) There is significant
evidence, alpha =0.05, that there is a difference in the proportions of boys assigned to the treatments (b)
There is not significant evidence, alpha =0.05, that there is a difference in the proportions of boys
assigned to the treatments (c) Statistically speaking the difference in the proportions of boys assigned to
the treatment is 0 (d) b and c.
Question 6
A clinical trial is conducted to investigate the effectiveness of an experimental drug in reducing preterm
delivery to a drug consigned standard care and to placebo. Pregnant women are enrolled and randomly
assigned to receive either the experimental drug, the standard drug or placebo. Women are followed
through delivery and classified as delivery preterm (>37 weeks) or not The data are shown below.
Is there a statistically significant difference in the proportions of women delivery preterm among the
THREE treatments groups? Apply the test of 5% level of significance.
1 df = 2
2. critical value = 5.991
3. computed value = 8.96
4. based on comparing the computed chi square with the critical values for the Chi square which of the
following is (are) true?
(a) there is statistically significant difference in the proportions of women delivering preterm among the
three treatments groups (b) there is not statistically significant difference in the proportions of women
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delivering preterm among the three treatments groups (c) the proportion are statistically the same (d) a
and c
Preterm delivery Experimental drug Standard drug Placebo
Yes 17 23 35
No 83 77 65
Question 7
The table below summarizes baseline characteristics of patients participating in a clinical trial. Which, if
any, baseline characteristics are significantly different (at the 0.05 level of significance) between
treatment groups (a) age (b) Total cholesterol (c) Diabetes (d) % female (e) a and b (f) c and d
Characteristic Placebo (n=125) Experimental (n=125 P
Men (+ - SD) age 54 + - 4.5 53 + - 4.9 0.7856
%female 39% 52% 0.0289
% less than high school
education
24% 22% 0.0986
% completing high
school
37% 36
% completing some
college
39% 42%
Mean (+ - SD) Systolic
blood pressure
136 + - 13.8 134 + - 12.4 0.4736
Mean (+ - SD) total
cholesterol
214 + - 24.9 210 +- 23.1 0.8954
% current smokers 17% 15% 0.5741
% with diabetes 8% 3% 0.0438
Question 8
An investigator conducts a study to investigate whether there is a difference in mean PEF in children with
chronic bronchitis are compared to those without. 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? Apply the appropriate test at alpha = 0.05
1. critical value = -1.677
2. computed t = -1.891
3. Based on comparing the critical t value to the computed t value which of the following is (are) true?
(a) There is statistical evidence of a lower mean PEF in children with bronchitis as compared to those
without (b) There is NOT statistical evidence of a lower mean PEF in children with bronchitis as
compared to those without (c) There are not enough data points to reach a conclusion (d) b and c.
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Group Number of children Mean PEF STD Dev PEF
Chronic Bronchitis 25 281 68
No chronic bronchitis 25 319 74
Question 9
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 are studied and their means PEF is 279 with a standard
deviation of 71. Is there statistical evidence of a lower mean PEF in children with chronic bronchitis?
Apply the appropriate test at alpha = 0.05
1. critical value = -1.685
2. computed z = -2.405
3. based on comparing the critical z value to the computed z value which of the following is (are) true?
(a) There is statistically significant evidence at alpha = 0.05 to show a lower mean PEF in children with
chronic bronchitis (b) There is NOT statistically significant evidence at alpha = 0.05 to show a lower mean
PEF in children with chronic bronchitis (c)There are not enough data points to reach a conclusion (d) b
and c
Question 10
The line of best fit can be defined as:
A. a line through a scatterplot that maximizes the distance from the line and the individual scatter plot
points.
B a line through a scatterplot that minimizes the distance from the line and the individual scatter plot
points.
C A scatter plot of the results of substituting independent variables into the regression equation
D a and a
E b and c
Question 11
An investigator wants to assess whether the use of a specific medication given to infants born
prematurely is associated with developmental delay, fifty infants who were given the medication
and fifty comparison infants who were also born prematurely but not given the medication will
be selected for the analysis. Each infant will undergo extensive testing at age 2 for various
aspects of development. Identify the type of study
Cohort Study
