5.3.23

The Physicians' Health Study is a very large, randomized study designed to "test the effects of low-dose aspirin... in the prevention of cardiovascular disease (CVD)." The subjects were 22,071 U.S. male physicians (aged 40-84 years, in the year 1982), who were randomly assigned to be in either the low-dose aspirin group or the placebo group.

Each participant was required to take the assigned pill every other day for five years. The study was double-blind. Of the 11,034 physicians who took the placebo, 189 suffered heart attacks during the study. Of the 11,037 physicians who took aspirin, 104 had heart attacks.

Organize the counts in a welllabeled 2 x 2 table. Placebo Aspirin Total Heart attack? Heart attack? Yes n 104 I 189 293