2.140 Aspirin and heart attacks

Does taking aspirin regularly help prevent heart attacks? “Nearly five decades of research now link aspirin to the prevention of stroke and heart attacks.” So says the Bayer Aspirin website, bayeraspirin.com. The most important evidence for this claim comes from the Physicians’ Health Study. The subjects were 22,071 healthy male doctors at least 40 years old. Half the subjects, chosen at random, took aspirin every other day. The other half took a placebo, a dummy pill that looked and tasted like aspirin. Here are the results.²⁸ (The row for “None of these” is left out of the two-way table.)

What do the data show about the association between taking aspirin and heart attacks and stroke? Use percents to make your statements precise. Include a mosaic plot if you have access to the needed software. Do you think the study provides evidence that aspirin actually reduces heart attacks (cause and effect)?