6 A Study is conducted comparing HDL cholesterol levels between men who exercise regularly and those who do not. The data are shown below. Generate a 95% confidence interval for the difference in mean HDL levels between men who exercise regularly and those who do not. 1. 2. 3. 4. Z 95% Confidence: Upper Limit 95% Lower Limit 95% 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 Regular Exercise Yes No N 35 120 Mean 48.5 56.9 Std Dev 12.5 11.9 Question 7 An investigator conducts a study to investigate whether there is a difference in mean PEF in children with chronic bronchitis (mean/cb) as compared to those with no chronic bronchitis (mean/ncb). Data on PEF are collected and summarized below. Assume alpha is 5%. N, mean, SD Cb 25, 281, 68 Ncb 25, 319, 74 1. Calculate the confidence interval for mean/cb - mean/ncb. 2. Compute mean/cb - mean/ncb: 3. Which of the following is true? a. There is statistical evidence of a different mean PEF in children with chronic bronchitis as compared to those without. b. There is statistical evidence of a difference in mean between the two groups. c. The confidence interval contains the difference in the means. d. A and C Group Chronic Bronchitis No Chronic Bronchitis Number of Children 25 25 Mean 281 319 Std Dev PEF 68 74 Question 8 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. 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=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 Serum Cholesterol between treatments New Drug and Placebo is essentially 0 d. B and C Mean (SD) Total Serum Cholesterol % Patients with Total Cholesterol less than 200 Question 9 New Drug (n=75) 185.0 (24.5) 78.0% Placebo (n=75) 204.3 (21.8) 65.0% Total Sample (n=150) 194.7 (23.2) 71.5% Average adult Americans are about one inch taller, but nearly a whopping 25 pounds heavier than they were in 1960, according to a new report from the Centers for Disease Control and Prevention (CDC). The bad news, says CDC is that average BMI (body mass index, a weight -for-height formula used to measure obesity) has increased among adults from approximately 25 in 1960 to 28 in 2002. Boston is considered one of America's healthiest cities - is weight gain since 1960 similar in Boston? A sample of n=25 adults suggested a mean increase of 17 pounds with a standard deviation of 8.6 pounds. Is Boston statistically significantly different in terms of weight gain since 1960? Apply the appropriate test at a 5% level of significance. 1. Critical t value +/2. Computed statistic: 3. Based on comparing the computed statistic to the critical value which of the following is (are) true? a. There is significant evidence, alpha=0.05, that the BMI for Boston residents is significantly different than 25. b. There is not significant evidence, alpha=0.05, that the BMI for Boston residents is significantly different than 25. c. Statistically speaking the difference between the BMI for Boston residents and a BMI of 25. Is 0. Question 10 A clinical trial is conducted to investigate the effectiveness of an experimental drug in reducing preterm delivery to a drug considered standard care and to placebo. Pregnant women ae enrolled and randomly assigned to receive either the experimental drug, the standard drug or placebo. Women are followed through delivery and classified as delivering preterm ( less than 37 weeks) or not. The data are shown below 1. 2. 3. 4. Df: Critical value: Computed value: Based on comparing the computed Chi Square value with the critical value for Chi Square which if the following is (are) true? a. There is statistically significant difference in the proportions of women delivering preterm among the three treatment groups b. There is not statistically significant difference in the proportions of women delivering preterm among the three treatment groups c. The proportions are statistically the same d. A and C Preterm Delivery Yes No Question 11 Experimental Drug 17 83 Standard Drug 23 77 Placebo 35 65 A randomized controlled trial is run to evaluate the effectiveness of a new drugh 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 statistic 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 ages of children assigned to the treatments. b. There is not significant evidence, alpha =0.05, that there is a difference in ages of children assigned to the treatments. c. Statistically speaking the difference in initial weights and weights after 6 weeks is 0 d. B and C Question 12 A study is designed to investigate whether there is a difference in response to various treatments in patients with rheumatoid arthritis. The outcome is patients self-reported effect of treatment. The data are shown below. Is there a statistically significant difference in the proportions of patients who show improvement between treatments 1 and 2. Apply the test at a 5% level of significance. 1. Critical 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, to show that there is a difference in the proportions of patients who show improvement between treatments 1 and 2. b. There is not significant evidence, alpha = 0.05, to show that there is a difference in the proportions of patients who show improvement between treatments 1 and 2 c. There is significant evidence, alpha = 0.05 to show that there is a no difference in the proportions of patients who show improvement between treatments 1 and 2. d. A and C Treatment 1 Treatment 2 Symptoms Worsened 22 14 No Effect 14 15 Symptoms Improved 14 21 Total 50 50 Question 13 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. 1. Upper Limit CI 2. Lower Limit CI Question 14 Regression equations can take the form: In the spaces next to the items below place the letter corresponding symbol for the equations. A. B. C. D. 1. 2. 3. 4. Y b0 b1 X Regression line slope: Predicted value: Independent variable: Y intercept: = b + b Question 15 Consider the following 4 graphs. If a regression equation were derived for each graph, which equation(s) would be able to most accurately predict Y values from X values? A. B. C. D. E. Graph A Graph B Graph C Graph D Graph B and D Question 16 The graph below shows what kind of relationship between the independent and depend variables; A. B. C. D. E. Positive inverse relationship Inverse relationship Positive relationship No relationship Not enough information Question 17 A national survey is conducted to assess the association between hypertension and stroke in persons over 75 years of age with a family history of stroke in persons over 75 years of age with family history of stroke. Development of stroke is monitored over a 5year follow-up period. The data are summarized below and the numbers are in millions. 1. Compute the cumulative incidence of stroke in persons over 75 years of age Cumulative Incidence 5 Years = 2. Compute the relative risk of stroke in hypertensive as compared to non-hypertensive persons Relative Risk = 3. Compute the odds ratio of stoke in hypertensive as compared to non-hypertensive person Odds Ratio = Hypertension No Hypertension Question 18 Developed Stroke 24 8 Developed Stroke 74 52 A case-control study is conducted to assess the relationship between heavy alcohol use during the first trimester of pregnancy and miscarriage. Fifty women who suffered miscarriage are enrolled along with 50 who delivered full term. Each participant's use of alcohol during pregnancy is ascertained. Heavy drinking is defined as 4 or more drinks on one occasion. The data are shown below. 1. Compute the odds of miscarriage in women with heavy alcohol use in pregnancy. Odds Heavy Use = 2. Compute the odds of miscarriage in women with no heavy alcohol use in pregnancy. Odds No Heavy Use = 3. Compute is the odds ratio for miscarriage as a function of heavy alcohol use. Odds ratio = Heavy Alcohol Use No Heavy Alcohol Use Miscarriage 28 72 Delivered Full Term 8 92 Question 19 A cohort study is conducted to assess the association between clinical characteristics and the risk of stroke. The study involves n=2.000 participants who ae free of stroke at the study start. Each participant is assessed at study start (baseline) and every year thereafter for five years. The following table displays data on hypertension status measured at baseline and hypertension status measured two years later. 1. Compute the prevalence of hypertension at baseline. Prevalence = 2. Compute the prevalence of hypertension at 2 years. Prevalence = 3. Compute the cumulative incidence of hypertension over 2 years. Incidence = Baseline: Not Hypertensive Baseline: Hypertensive Question 20 2 Years: Not Hypertensive 1700 90 2 Years: Hypertensive 296 414 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. Consider the study described in problem 8, what is the 2-year cumulative incidence of hypertension? Cumulative Incidence 2 Years =