Refer to the Federal Trade Commission (FTC) 1998

"Price Check" study of electronic checkout scanners, Exercise 4.30

(p. 192). The FTC inspected 1,669 scanners at retail stores and supermarkets by scanning a sample of items at each store and determining if the scanned price was accurate. The lTC gives a store a "passing" grade if 98% or more of the items are priced accurately. Of the 1,669 stores in the study, 1,185 passed inspection.

a. Find a 90% confidence interval for the true proportion of retail stores and supermarkets with electronic scanners that pass the FTC price-check test.

Interpret the result.

b. In 1996, the FTC found that 45% of the stores passed inspection. Use the interval from part a to determine whether the proportion of stores that pass inspection in 1998 exceeds .45.