Angioplasty’s benefits challenged. Refer to the study of patients with substantial blockage of the arteries presented at the 2007 Annual Conference of the American College of Cardiology. 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 in order to estimate the difference in heart attack rates to within .015 with 95% confidence? (Use summary data 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.
Angioplasty’s benefits challenged. Each year, more than 1 million heart patients undergo an angioplasty. The benefits of an angioplasty were challenged in a recent study of 2,287 patients (2007 Annual Conference of the American College of Cardiology, New Orleans). All the patients had substantial blockage of the arteries, but were medically stable. All were treated with medication such as aspirin and beta-blockers. However, half the patients were randomly assigned to get an angioplasty and half were not. After five years, the researchers found that 211 of the 1,145 patients in the angioplasty group had subsequent heart attacks, compared with 202 of 1,142 patients in the medicationonly group. Do you agree with the study’s conclusion that “There was no significant difference in the rate of heart attacks for the two groups”? Support your answer with a 95% confidence interval.
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