Suppose we assume that the incidence of MI is .005 per year among participants who actually take placebo and that aspirin prevents 20% of MIs (i.e. relative risk = p1/p2=0.8) We also assume that the duration of the study is 5 years and that the dropout rate in the aspirin group=10% and the drop in rate in the placebo group=5%. How many participants need to be enrolled in each group to achieve 80% power using a two-sided test with significance level =.05

How many participants need to be enrolled in each group to have a 90% chance of detecting a significant difference using a two sided test with α =0.05 if compliance is perfect?