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Unformatted text preview: Statistics 403 Problem Set 11 Due in lab on Friday, December 10th 1. Suppose we are conducting a study to assess whether heavy drinking is associated with the development of pancreatic cancer. We identify 50 pancreatic cancer cases from a medical center and determine which among them are heavy drinkers. We also identify 50 agematched people without pancreatic cancer and determine which among them are heavy drinkers. As a result, we obtain the following table PC Not PC HD 19 9 Not HD 31 41 (a) What is the pvalue for the null hypothesis that there is no association between heavy drinking and the occurance of pancreatic cancer? Solution: The log odds ratio is log(19) + log(41) log(9) log(31) ≈ 1 . 03 . The standard error of this estimate is p 1 / 19 + 1 / 41 + 1 / 9 + 1 / 31 ≈ . 47 . The standardized log odds ratio (Zscore) is 1 . 03 / . 47 ≈ 2 . 2. Thus the pvalue is P (  Z  >  Z obs ) = 2 P ( Z < 2 . 2) ≈ . 03 . (b) Construct a 95% confidence interval for the population log odds ratio. Solution: The 95% CI is the estimate plus or minus two times its standard error, thus the CI is (1 . 03 2 · . 47 , 1 . 03 + 2 · . 47) = (0 . 09 , 1 . 97) ....
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 Winter '12
 KerbyShedden
 Statistics, Null hypothesis, Statistical hypothesis testing, Pancreatic Cancer, 80%

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