Recall that half the patients were randomly assigned to get an angioplasty and half were not. The researchers compared the proportion of patients with subsequent heart attacks for the two groups and reported no significant difference between the two proportions. Although the study involved over 2,000 patients, the sample size may have been too small to detect a difference in heart attack rates.
a. How many patients must be sampled in each group to estimate the difference in heart attack rates to within .015 with 95% confidence? (Use summary data from Exercise 8.56 in your calculation.)
b. Comment on the practicality of carrying out the study with the sample sizes determined in part a.
c. Comment on the practical significance of the difference detected in the confidence interval for the study, part a.
For Information: Refer to the study of patients with substantial blockage of the arteries presented at the 2007 Annual Conference of the American College of Cardiology, Exercise 8.56.