Accuracy of price scanners at Wal-Mart. Refer to Exercise 7.129

(p. 387) and the study of the accuracy of checkout scanners at Wal-Mart stores in California. Recall that the National Institute for Standards and Technology (NIST)

mandates that, for every 100 items scanned through the electronic checkout scanner at a retail store, no more than 2 should have an inaccurate price. A study of random items purchased at California Wal-Mart stores found that 8.3% had the wrong price (Tampa Tribune, Nov. 22, 2005). Assume that the study included 1,000 randomly selected items.

a. Identify the population parameter of interest in the study.

b. Set up H0 and Ha for a test to determine whether the true proportion of items scanned at California Wal-Mart stores exceeds the 2% NIST standard.

c. Find the test statistic and rejection region (at a = .052 for the test.

d. Give a practical interpretation of the test.

e. What conditions are required for the inference made in part d to be valid? Are these conditions met?