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Chapter 13 Homework

Design and Analysis Techniques for Epidemiologic Studies

1. In a 1985 study of the relationship between contraceptive use and infertility, 89 of 283 infertile women, compared with 640 of 3833 control (fertile) women, had used an intrauterine device (IUD) at some time in their lives.

(a) Use the normal-theory method to test for significant differences in contraceptive-use patterns between the two groups.

(b) Use the contingency-table method to perform the test in part (a).

(c) Compare your results from part (a) and (b).

(d) Compute a 95% confidence interval for the difference in the proportion of women who have ever used IUDs between the infertile and fertile women in part (a).

(e) Compute the OR in favor of ever using an IUD for infertile women vs. fertile women.

(f) Provide a 95% confidence interval for the true OR corresponding to your answer in part (e).

(g) What is the relationship between your answers to part (b) and (f).

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2. The data in the table below were presented relating body mass index (BMI) to progression of advanced age-related macular degeneration (AMD), a common eye disease in the elderly that results in significant visual loss.

Association between BMI and progression of AMD BMI Progression Non-progression < 25 72 423 ≥ 25 209 762

(a) What is the attributable risk (AR) of high BMI (≥ 25) for progression of AMD?

(b) Provide a 95% confidence interval about this estimate.

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