A statistical analysis that combines information from several studies is called a meta analysis. A meta analysis compared aspirin with placebo on incidence of heart attack and of stroke, separately for men and for women

(J. Am. Med. Assoc., 295: 306–313, 2006). For the Women’s Health Study, heart attacks were reported for 198 of 19,934 taking aspirin and for 193 of 19,942 taking placebo.

a. Construct the 2 × 2 table that cross classifies the treatment (aspirin, placebo) with whether a heart attack was reported (yes, no).

b. Estimate the odds ratio. Interpret.

c. Find a 95% confidence interval for the population odds ratio for women.
Interpret. (As of 2006, results suggested that forwomen, aspirinwas helpful for reducing risk of stroke but not necessarily risk of heart attack.)