Checkout scanners - Proportion problem. The Federal Trade Commission (FTC) conducted a study in 1998 of checkout scanners. 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 FTC gave a store a passing grade if 98% or more of the items are priced correctly. Of the 1,669 stores in the study, 1,185 passed inspection. You have everything you need to do a confidence interval, with a z-table.
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 in part a to determine whether the proportion of stores that pass inspection in 1998 exceeds .45.