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· A study is run comparing HDL cholesterol levels between men who exercise regularly and those who do not. The data are shown below.
Regular Exercise
N
Mean
Std Dev
Yes
35
48.5
12.5
No
120
56.9
11.9
Generate a 95% confidence interval for the difference in mean HDL levels between men who exercise regularly and those who do not
1. Z 95% Confidence:
2. Upper Limit 95% CI
3. Lower Limit 95% CI
4. Based on the examination of the upper and lower limits of the confidence interval for the mean HDL levels which of the following is (are) true.
A. There is statistical evidence of a difference in mean HDL levels between men who exercise regularly and those who do not.
B. There is not statistical evidence of a difference in mean HDL levels between men who exercise regularly and those who do not.
C. The confidence interval contains the mean HDL level.
D. B and C
· 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). The mean age of children assigned to the new drug is 12.4 with a standard deviation of 3.6 years. The mean age of children assigned to the placebo is 13.0 with a standard deviation of 4.0 years. Is there a statistically significant difference in ages of children assigned to the treatments? Apply the two sample z test at a 5% level of significance.
1. Critical z value= +/-
2. Computed statistic=
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 significantly different in ages of children assigned to the treatments.
B. There is not significant evidence, alpha=0.05, that there is significantly difference in ages of children assigned to the treatments
C. Statistically speaking the difference in initial weights after 6 weeks is 0
D. B and C
· The following are body mass index (BMI) scores measured in 12 patients who are free of diabetes and 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=
Lower limit of CI=
· A clinical trial is conducted to evaluate the effectiveness of a new drug to prevent preterm delivery. A total of n=250 pregnant women agree to participate and are randomly assigned to receive either the new drug or a placebo and followed through the course of pregnancy. Among 125 women receiving the new drug, 24 deliver preterm and among 125 women receiving the placebo, 38 deliver preterm. Construct a 95% confidence interval for the difference in proportions of women who deliver preterm
Upper limit CI=
Lower limit CI=
· 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 boys assigned to the placebo. Is there a statistically significant difference in the proportion of boys assigned to the treatments? Apply the appropriate test at a 5% level of significance
1. Critical value=+/-
2. Computed statistics=
3. Based on comparing the computed statistic to the critical value which of the following is (are) true?
A. There is significant evidence alpha=.05 that there is a difference in the proportions of boys assigned to the treatments
B. There is not significant evidence alpha=.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 treatments is 0
D. B and C
· The following data were collected in a clinical trial to compare a new drug to a placebo for its effectiveness in 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)
Mean (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%
1. Upper limit of CI=
2. Lower limit of CI=
3. Based on the confidence interval which of the following is (are) true?
a. There is significant evidence alpha-.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=.05 to show that there is a difference in total serum cholesterol between treatments new drug and placebo
c. The difference between total serum cholesterol between treatments new drug and placebo is essentially 0
d. B and C
· A total of 300 participants are selected for a study of risk factors for cardiovascular disease. At baseline (study start) 48 are classified as hypertensive. At one year an additional 24 have developed hypertension and at 2 years another 16 have developed hypertension. What is the prevalence of hypertension at 2 years in the study?
1. Prevalence 2 years=
2. What is the 2 year cumulative incidence of hypertension? Cumulative incidence 2 years=
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