Exam 3 with Answers 2006 - BIOE 301 Exam 2 April 11, 2006...

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BIOE 301 Name: Exam 2 Time Started: April 11, 2006 Time Finished : The exam consists of 7 questions on 13 pages. Please note the following ground rules: This is an open book, open note exam. The total time to work the exam is 1.5 hours. You are not allowed to consult any people other than the course instructor or TAs regarding questions about the exam. Show all work to receive credit. Clearly organize your work and draw a box around your final answers. NEATNESS COUNTS! Good Luck! Problem 1 (20): Problem 2 (20): Problem 3 (15): Problem 4 (10): Problem 5 (15): Problem 6 (10): Problem 7 (10): Extra Credit (2): Total (100): Page 1

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1. You are designing a study to test a new implantable artificial kidney for patients with end-stage renal disease. You divide your patients into two groups: one will receive an implanted artificial kidney, the other will receive triweekly hemodialysis (standard of care in end stage renal disease). Your primary endpoint is mortality for all causes at one year, a secondary endpoint is patient quality of life at one year, which will be assessed via questionnaire. a. What is a type I error? What are the possible consequences of making a type I error in this study? Mistaken conclusion that there is a difference between two groups when difference doesn’t exist. Some people might receive an artificial kidney when it is no better (or possibly worse) than dialysis. b. What is a type II error? What are the possible consequences of making a type II error in this study? Mistaken conclusion that there is no difference between two groups, when in fact there is a difference. People might not receive a beneficial new treatment. It might be abandoned and not studied further. c. Define the p-value. Probability of making a type I error. d. Define power (if you use Greek letters in your definition, you must define these as well). Power = 1 – probability of making a type II error = 1 – beta = probability of NOT making a type II error e. Why would blinding be difficult in this study? One group of patients is undergoing a surgery, the other is being hooked up to a machine three times a week – they’re probably going to figure out which group they’re in f. Which of your endpoints is more likely to be affected by a lack of blinding? Patient quality of life – because it’s more subjective Page 2
g. Assuming you expect 30% mortality at one year for the control group and 20% for the treatment group, what sample size would be required to achieve 80% power? You may wish to use the nomogram below. What p-value should you use? Justify this value. Page 3

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2. Cardiovascular disease is the leading cause of death in the US. a. What are the two major form of cardiovascular disease (CVD) and which form is more common in the US? Ischemic heart disease and stoke are the two major forms of the disease which affect almost a quarter of
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Exam 3 with Answers 2006 - BIOE 301 Exam 2 April 11, 2006...

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