Chapter 11.1, Problem 10E

Consumer Reports uses a 100-point customer satisfaction score to rate the nation’s major chain stores. Assume that from past experience with the satisfaction rating score, a population standard deviation of σ = 12 is expected. In 2012, Costco, with its 432 warehouses in 40 states, was the only chain store to earn an outstanding rating for overall quality (Consumer Reports, March 2012). A sample of 15 Costco customer satisfaction scores follows.

1. a. What is the sample mean customer satisfaction score for Costco?
2. b. What is the sample variance?
3. c. What is the sample standard deviation?
4. d. Construct a hypothesis test to determine whether the population standard deviation of σ = 12 should be rejected for Costco. With a .05 level of significance, what is your conclusion?