How large sample is needed to achieve power

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Suppose the incidence rate of MI ( myocardial infarction) per year was 5 per 1000 among 45 to 54 year old men in 1990. To look at changes in incidence over time, 5000 45 to 54 year old men were followed for 1 year starting in 2000. Fifteen new cases of MI were found. A. Suppose we eventually plan to accumulate 50 MI cases during the period 2000-2005. Assume that the 24-hour case-fatality is truly 20% during this period. How much power would such a study have in distinguishing between case-fatality rates in 1990 and 2000-2005 if a two-sided test with significance level .05 is planned? B. How large a sample is needed in the previous problem to achieve 90% power?

Reference no: EM13143243

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