In texas, researchers gave a cholesterol-reducing drug to 2,335 people and an inactive substitute (placebo) to 2,081. most of the volunteers were men who had normal cholesterol levels and no history of heart disease. after 5 years, 97 people getting the placebo had suffered heart attacks compared to only 57 people who had received the actual drug. the researchers are recommending that to prevent heart attacks, all people (even those without high cholesterol) takes these cholesterol-reducing drugs. in addition to the information above, what is another piece of information that the researchers must have before support for the recommendation can be justified?
a. were eating habits of the two groups similar?
b. how does a heart attack affect cholesterol levels?
c. did the heart attacks result in deaths?
d. what chemical is in the placebo?