Putting It Together: Women, Aspirin, and Heart Attacks In a famous study by the

Chapter 12, Problem 21

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Putting It Together: Women, Aspirin, and Heart Attacks In a famous study by the Physicians Health Study Group from Harvard University from the late 1980s, 22,000 healthy male physicians were randomly divided into two groups; half thephysicians took aspirin every other day, and the others were givena placebo. Of the physicians in the aspirin group, 104 heart attacksoccurred; of the physicians in the placebo group, 189 heart attacksoccurred. The results were statistically significant, which led tothe advice that males should take an aspirin every other dayin the interest of reducing the chance of having a heart attack.Does the same advice apply to women?In a randomized, placebo-controlled study, 39,876 healthywomen 45 years of age or older were randomly divided into twogroups. The women in group 1 received 100 mg of aspirin everyother day; the women in group 2 received a placebo every otherday. The women were monitored for 10 years to determine ifthey experienced a cardiovascular event (such as heart attack orstroke). Of the 19,934 in the aspirin group, 477 experienced a heartattack. Of the 19,942 women in the placebo group, 522 experienceda heart attack. Source: Paul M. Ridker et al. A Randomized Trial ofLow-Dose Aspirin in the Primary Prevention of Cardiovascular Disease inWomen. New England Journal of Medicine 352:12931304.(a) What is the population being studied? What is the sample?(b) What is the response variable? Is it qualitative orquantitative?(c) What are the treatments?(d) What type of experimental design is this?(e) How does randomization deal with the explanatory variablesthat were not controlled in the study?(f) Determine whether the proportion of cardiovascular eventsin each treatment group is different using a two-sampleZ-test for comparing two proportions. Use the a = 0.05 levelof significance. What is the test statistic?(g) Determine whether the proportion of cardiovascular eventsin each treatment group is different using a chi-square testfor homogeneity of proportions. Use the a = 0.05 level ofsignificance. What is the test statistic?(h) Square the test statistic from part (f) and compare it to thetest statistic from part (g). What do you conclude?