Question 1
Suppose you want to estimate the difference between two population proportions correct to within 0.03 with probability 0.90. If prior information suggests that p
1 ≈ 0.4 and p
2 ≈ 0.8, and you want to select independent random samples of equal size from the populations, how large should the sample sizes be?
◦ n
1 = n
2 = 1203
◦ n
1 = n
2 = 963
◦ n
1 = n
2 = 1925
◦ n
1 = n
2 = 1708
Question 2
Two surgical procedures are widely used to treat a certain type of cancer. To compare the success rates of the two procedures, random samples of surgical patients were obtained and the numbers of patients who showed no recurrence of the disease after a 1-year period were recorded. The data are shown in the table.
How large a sample would be necessary in order to estimate the difference in the true success rates to within .10 with 95% reliability?
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