hw1key - BIOST/EPI 513 Spring Quarter 2011 Dr. McKnight...

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1 BIOST/EPI 513 Spring Quarter 2011 Dr. McKnight HOMEWORK 1 KEY See Appendix I for STATA commands and Appendix II for output. 1. Use Stata to examine the evidence for association between country of residence and prevalence of oncogenic HPV (Types 16 and 18) using the cross-sectional data presented on page 19 of the class notes. Then prepare the following to hand in: (a) Choose an association measure (RD, RR or OR) that you think best describes the association between country and the prevalence of HPV. State your choice and give a brief (one-sentence) justification for it. RD is the most natural way of comparing disease prevalence between countries, since together with the female population of each country in this age range, it gives an idea of how many more or fewer women are infected with oncogenic HPV. If the data were collected to compare the effect of vaccination programs in the two countries, RR might also be useful. There is no need to use the OR here. (b) Using at most two sentences, write a summary, appropriate for the results section of a scientific paper, that describes the findings from your statistical analysis of these data. Be sure to use information in the data about your association measure of choice. Our data provided strong evidence that oncogenic HPV (Types 16 and 18) was associated with the country of residence ( p= 0.036). The estimated disease risk was 0.019 (95% CI: 0.0012, 0.037) lower among American women aged 15-25 years than among Brazilian women of the same age range. 2. In the CARE case-control study discussed in class, investigators also examined how the risk of breast cancer was associated with prior use of combination oral contraceptives. A 2×2 table of data is given below. Current OC use No OC use Total Cases 200 1032 1232 Controls 172 980 1152 Use Stata to examine the evidence for association between current OC use and the incidence of breast cancer, using these retrospective data. Then prepare the following to hand in: (a) Choose an association measure (RD, RR or OR) that you think best describes the association between current combination OC use and the risk of developing breast cancer. State your choice and give a brief (one-sentence) justification for it. OR is best for describing the association between risk of breast cancer and prior OC use, because
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This note was uploaded on 02/09/2012 for the course STAT 513 taught by Professor Barbaramc.knight during the Spring '11 term at University of Washington.

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hw1key - BIOST/EPI 513 Spring Quarter 2011 Dr. McKnight...

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