Subjects with pre‑existing cardiovascular symptoms who were receiving sibutramine, an appetite suppressant, were found to be at increased risk of cardiovascular events while taking the drug. The study included 9804 overweight or obese subjects with pre‑existing cardiovascular disease and/or type 2 diabetes. The subjects were randomly assigned to sibutramine ( 4906 subjects) or a placebo ( 4898 subjects) in a double‑blind fashion. The primary outcome measured was the occurrence of any of the following events: nonfatal myocardial infarction or stroke, resuscitation after cardiac arrest, or cardiovascular death. The primary outcome was observed in 561 subjects in the sibutramine group and 490 subjects in the placebo group. a. Find the proportion of subjects experiencing the primary outcome for both the subitramine and placebo group?
b. Can we safely use the large-sample confidence interval for comparing the proportions of subitramine and placebo subjects who experienced the primary outcome? Explain.
c. Give a 95% confidence interval for the difference between the proportions of subitramine and placebo subjects who experienced the primary outcome?