The per-store daily customer count (i.e., the mean number of customers in a store in one day) for a nationwide convenience store chain that operates nearly 10,000 stores has been steady, at 900, for some time. To increase the customer count, the chain is considering cutting prices for coffee beverages. Management needs to determine how much prices can be cut in order to increase the daily customer count without reducing the gross margin on coffee sales too much. You decide to carry out an experiment in a sample of 24 stores where customer counts have been running almost exactly at the national average of 900. In 6 of the stores, a small coffee will be $0.59, in another 6 stores the price will be $0.69, in a third group of 6 stores, the price will be $0.79, and in a fourth group of 6 stores, the price will now be $0.89. After four weeks, the daily customer count in the stores is stored in CoffeeSales.
a. At the 0.05 level of significance, is there evidence of a difference in the daily customer count based on the price of a small coffee?
b. Compare the results of (a) with those of Problem 11.11 (a) on page 428.