7.87 Credit card fees.
The bank in Exercise 7.30 (page 377) tested a new idea on a sample of 125 customers. Suppose that the bank wanted to be quite certain of detecting a mean increase of in the credit card amount charged, at the significance level. Perhaps a sample of only customers would accomplish this. Find the approximate power of the test with for the alternative as follows:
7.87
(a) . (b) Reject when , or when . (c) 0.5398. This power is not sufficient, we should recommend that the bank use more customers to increase power.