Final_BIOS7010E.pdf

NAME _____________________________ Introductory Biostatistics BIOS 7010E Final Exam SHOW ALL WORK AND INTERMEDIATE CALCULATIONS.

1. The following is an ANOVA table from a regression analysis. Review the result and fill in the missing entries identified by a serial number and asterisks in bold-face. (Show intermediate calculation to gain partial credit) (15 points) Source DF Sum of Squares Mean Square F Value P Value Regression (1)* 138.327 (2)* (3)* <.0001 Residual 79 (4)* (5)* Total 80 236.558 R-Square (6)* Root MSE (7)* Answser: (1) (2) (3) (4) (5) (6) (7)

2. Kapitulnik et al. (1976; Clinical Pharmaceuticals and Therapeutics 20 , 557-564) measured the metabolism of the drug zoxazolamine in the placentas of 13 women who smoked and 11 women who did not smoke during pregnancy. All 24 women were volunteers, and whether or not they smoked during pregnancy was controlled by women and not the authors of the study. For each woman, zoxazolamine hydroxylase production was measured in nmol/g/hour. a. The following shows the results of a preliminary analysis of the data: Based on the results of this analysis, are any assumptions of the two sample t-test violated? If so, what assumption is violated? Present the evidence to back up your conclusion. (4 points) b. The following shows the results of two different methods for analyzing the data: Method 1

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Method 2 Based on your conclusions from part (a), which method is more appropriate? (3 points) (A) Method 1 (B) Method 2 c. Present the 95% confidence interval for the difference between the treatment means. (3 points) d. What can you conclude from the analysis in part (b)? Use only the results from the selected method. (3 points) e. Can we draw causal inferences from the results of this study? (3 points) (A)Yes (B)No

3. HbsAg is a surface antigen of the Hepatitis-B-Virus (HBV) which indicates current Hepatitis B infection. Seropositivity of HbsAg in patients with lymphoproliferative disorders and a control groups were obtained. Results appear in the table below. Group Patients Controls Total HbsAg positive 21 40 61 HbsAg negative 313 762 1075 Total 334 802 1136 a. What is the odds ratio for patients relative to controls? (3 points) b. What is the relative risk of HbsAg positivity for patients relative to controls? (3 points) c. Under the assumption of independence, what is the expected number of HbsAg positives among the controls? (3 points)

4 . A study was carried out to investigate the effects of speed bumps on child pedestrian injuries. A total of 100 children reporting to the emergency room of Metropolis hospital as a result of being struck by a motor vehicle were recruited into the study. Each traffic accident case was matched to a control by age, gender, and date of emergency room visit of children reporting the hospital for reasons other than having been struck by a motor vehicle. For each case and control, it was determined whether or not the child lived within one block of a speed bump. a. Is this a prospective or retrospective study? (Check only one) (3 points) (A)Prospective (B)Retrospective b . Which is the most appropriate method to test the hypothesis that the presence/absence of a speed bump is independent of whether we are looking at a motor vehicle accident case, or a non- motor vehicle accident control? (Check only one) (3 points) (A)Paired t-test (B)Two-sample t-test (C) McNemar’s test (D) Pearson’s Chi -square test c . Can we draw causal inferences from the results of this study? (Check only one) (3 points) (A)Yes (B)No

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5 . Lin et al. (2008; American Journal of Epidemiology 168 , 73-79) carried out a case-control study designed to assess the effects of the asthma medication bronchodilators on gastroschisis, a birth defect. Gastroschisis cases were identified from birth centers in eight states (Arkansas, California, Georgia, Iowa, Massachusetts, New Jersey, New York and Texas), and controls with no birth defects were randomly sampled from the same birth centers. The following output shows the results of the data analysis: Here, defect is coded "1" for gastroschisis cases, and "0" for non-birth defect controls, and medication is coded "1" if the mother uses a bronchodilator and "0" if not. a . What is the expected frequency of subjects exposed to the medication(bronchodilator) and also have birth defect (gastroschisis)? (3 points)

b . What can you conclude from the results of the data analysis? (4 points) c . Can we draw causal inferences from the results of this study? (Check only one) (3 points) (A)Yes (B)No 6 . Carbon dioxide (CO2 ) emissions were measured each year between 1971 and 1998 in London, United Kingdom. The following computer output shows the results of a simple linear regression predicting CO2 emissions as a function of percent traffic volume (relative to 1970).

a . Give the fitted regression line: (3 points) b . What is the predicted CO2 emissions for a traffic volume of 250? (3 points) c . What can you conclude from the results of the above data analyses? (4 points)

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7 . Which of the following are nonparametric tests? Check all that apply. (3 points) (A)Chi-Square test (B)Wilcoxon Signed-Rank test (C)Wilcoxon Rank-Sum test (D) McNemar’s test (E)Paired t-test (F)Two-sample t-test 8 . Under what circumstance(s) is a nonparametric test more appropriate than a parametric test? (3 points) 9 . Which of the following tests are appropriate for independent samples? Check all that apply. (3 points) (A)Chi-Square test (B)Wilcoxon Signed-Rank test (C)Wilcoxon Rank-Sum test (D) McNemar’s test (E)Paired t-test (F)Two-sample t-test

10 . A medical device manufacturer wishes to test the quality of their automated machine for measuring blood glucose of diabetes patients. A total of 47 diabetes patients were recruited into the study. For each patient, plasma glucose was measured both with the new device, and by a standard meter using test strips. The following summary statistics were obtained: Device Automated Standard Standard-Automated n 47 47 47 𝑥̅ 107.4 110.3 2.9 median 106.9 110.5 3.6 s 13.1 12.9 1.5 Which of the following procedures should be used to test for the efficacy of the new device? Check only one. (4 points) (A)One-Sample t-test (B)Paired t-test (C)Wilcoxon Signed-Rank (D)Two-Sample t-test (E)Wilcoxon Rank-Sum

11 . It has been suggested that pregnant women with hypertension will tend to have higher rates of complications than women without hypertension. To investigate this, records of 190 births, randomly selected from the files of the Mars City Memorial Hospital were used to crosstabulate hypertensive status and presence/absence of complications. The following data were obtained: Hypertension Complications Yes No Total Present 23 55 78 Absent 12 100 112 Total 35 155 190 a. What is the estimated proportion of birth complications among women with hypertension ( p 1)? (3 points) b. What is the estimated proportion of birth complications among women without hypertension ( p 2)? (3 points) c. Please provide the 95% confidence interval for the risk difference p 1 − p 2. (3 points)

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12. If the probability of two events happening together is equal to the product of the probabilities of each happening alone, then the events are (Check only one): (3 points) (A)Mutually exclusive (B)Independent (C)Equally likely (D)Indeterminate 13. Investigators wish to study a rare condition that afflicts 0.01% of the population. The objective will be to evaluate whether the mean blood serum levels of a particular protein are the same in individuals with the condition as they are in individuals without the condition. Both individuals with the condition and individuals without the condition need to be included in the study. They have enough funding to examine serum samples from n=100 people. What type of study design would be recommended in this setting? (Check only one) (3 points) (A)Simple random sample design (B)Case control design (C)Phase I clinical trial design (D)Crossover design 14. Consider the setting of evaluating a diagnostic test to detect the presence of a disease. If the area under the receiver operating characteristic curve (AUC) is 0.50, then one can conclude that the diagnostic test will be (Check only one): (3 points) (A)Perfectly accurate (B)Highly accurate (C)Moderately accurate (D)Completely useless