Researchers want to investigate whether taking aspirin regularly reduces the risk of a heart attack. 400 men between the ages of 50 and 84 are recruited as participants. The men are divided randomly into two groups: one group will take aspirin, and the other group will take a placebo. Each man takes one pill each day for three years, but he does not know whether he is taking aspirin or the placebo. At the end of the study, researchers count the number of men in each group who have had heart attacks.
Identify the following values for this study: population, sample, experimental units, explanatory variable, response variable, treatments.
OpenStax Statistics, 1.4 Experimental Design and Ethics, exercise 1