A designed experiment in the medical field involving human subjects is referred to as a clinical trial . One recent clinical trial was designed to determine the potential of using aspirin in preventing heart attacks. Volunteer physicians were randomly divided into two groups: the treatment group and the control group. Each physician in the treatment group took one aspirin tablet a day for one year, while the physicians in the control group took an aspirin-free placebo made to look identical to an aspirin tablet. Since the physicians did not know to which group—

treatment or control—they were assigned, the clinical trial is called a blind study .

Assume that 20 physicians volunteered for the study. Use a random-number generator to randomly assign half of the physicians to the treatment group and half to the control group.