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PU 515 Applied Biostatistics Final Exam




Question;PU 515;Applied Biostatistics;Final Exam;1. 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;2. Consider the data in Problem #1. 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?;3. 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 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 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.;4. Consider the data presented in problem #4.;Previous studies have shown that approximately 32% of women deliver prematurely;without treatment. Is the proportion of women delivering prematurely;significantly higher in the placebo group? Run the test at a 5% level of;significance.;PU 515;Applied Biostatistics;Final Exam;5. 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.;6. A clinical trial is run to assess the;effects of different forms of regular exercise on HDL levels in persons between;the ages of 18 and 29. Participants in the study are randomly assigned to one of;three exercise groups - Weight training, Aerobic exercise or Stretching/Yoga ?;and instructed to follow the program for 8 weeks. Their HDL levels are measured;after 8 weeks and are summarized below.;Exercise Group;N;Mean;Std Dev;Weight Training;20;49.7;10.2;Aerobic Exercise;20;43.1;11.1;Stretching/Yoga;20;57.0;12.5;Is there a significant difference in mean HDL;levels among the exercise groups? Run the test at a;5% level of significance. HINT: SSwithin =;21,860.;7. Consider again the data in problem #6. Suppose;that in the aerobic exercise group we also measured the number of hours of;aerobic exercise per week and the mean is 5.2 hours with a standard deviation;of 2.1 hours. The sample correlation is -0.42.;a) Is there evidence of a significant;correlation between number of hours of exercise per week and HDL cholesterol;level? Run the test at a 5% level of significance.;b) Estimate the equation of the regression;line that best describes the relationship between number of hours of exercise;per week and HDL cholesterol level (Assume that the dependent variable is HDL;level).;c) Estimate the HDL level for a person who;exercises 7 hours per week.;d) Estimate the HDL level for a person who;does not exercise.;PU 515;Applied Biostatistics;Final Exam;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.;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%;9. A small pilot study is conducted to;investigate the effect of a nutritional supplement on total body weight. Six;participants agree to take the nutritional supplement. To assess its effect on;body weight, weights are measured before starting the supplementation and then;after 6 weeks. The data are shown below. Is there a significant increase in;body weight following supplementation? Run the test at a 5% level of;significance.;Subject;Initial Weight;Weight after 6 Weeks;1;155;157;2;142;145;3;176;180;4;180;175;5;210;209;6;125;126;10. Answer True or False to each of the;following;a) The margin of error is always greater than;or equal to the standard error.;b) If a test is run and p=0.0356, then we can;reject H0 at?=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 means is (2.1 to 4.5), there is no significant difference in means.


Paper#60246 | Written in 18-Jul-2015

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