Investigators followed a population of 2,000 women aged over 65 years who did not have osteoporosis, over a 10-year period and measured the number of cases of osteoporosis diagnosed during that time-period. The investigators were interested in the effect of regular exercise on the development of osteoporosis. They divided the women into two groups: 1,000 women who exercised (exposed) and 1,000 women who did not exercise regularly (unexposed).
During the 10-year study period, investigators recorded 800 cases of osteoporosis, 300 in those women who exercised regularly and 500 in those who did not. Thu number of person-years at risk was 8,350 in the exposed group and 6,950 in the unexposed group
question: a) calculate the risk ratio, odds ratio and incidence rate ratio for the effect of regular excercise on osteoporosis in these women and provide a one-sentence interpretation for each result
b) contrast the findings of these measures of association, and discuss which measure is most appropiate.