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Unformatted text preview: BIOST / EPI 513 Spring Quarter 2011 Dr. McKnight HOMEWORK 2 Due in the class online drop box at 9pm, Monday, April 11, 2011 Please do not turn in any computer output, other than the scatterplot requested in problem 5, with this homework. 1. Data from the cancer and steroid hormone (CASH) study, a case-control study examining the the association between oral contraceptive (OC) use and the risk of breast cancer, are given in the table below. Table entries are total counts of case and control women in each of five age groups, and counts of women in each group with prior exposure to oral contraceptives. Cases Controls Age Group Total OC users Total OC users 20-24 15 15 106 74 25-29 126 109 169 148 30-34 382 341 429 378 35-39 700 605 590 502 40-44 865 632 771 560 Using methods we have covered in class, analyze these data to determine how strongly the data in this table support the hypothesis that oral contraceptives are associated with breast cancer incidence in young women. Then turn in answers to the following questions: (a) What is the appropriate measure of association between OC use and breast cancer status for these data? In one sentence, why? (b) Provide an estimate of this association measure, with 95% confidence interval. (c) Test the hypothesis that there is no association between OC use and breast cancer risk. i. State the name of the hypothesis test you use. ii. Give the value of the test statistic. iii. Name the probability distribution to which you compare the value of the statistic to obtain a P-value. iv. Give the P-value (d) In one or two sentences, present the results of your analysis as you would in the results section of a scientific paper reporting these data....
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