Nokea
Identify the type of study design described: A random sample of middle-aged sedentary women was selected from four census tracts, and each subject was examined for evidence of osteoporosis. Those found to have the disease were excluded. All others were randomly assigned to either an exercise group, which followed a two-year program of systematic exercise, or a control group, which had no exercise program. Both groups were observed semiannually for incidence of osteoporosis.
Correct Answer: C
Rationale: This is a randomized controlled trial evaluating preventive measures.