Consumer report uses 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 = 12 is expected. A sample of 15 Costco customer satisfaction scores follows:

90	83	82
97	85	66
88	84	95
96	95	94
82	78	64

What is the sample mean customer satisfaction score for Costco?

What is the sample variance?

What is the sample standard deviation?

Use = 0.05 level of significance to construct the the confidence interval for the population standard deviation .

Conduct a hypothesis test to determine whether the population standard deviation of = 12 should be rejected for Costco. Use = 0.05 level of significance , what is your conclusion?