Question

10.45 As mentioned in Exercise 10.31, Quadro Corporation has two supermarkets in a city. The com pany's quality control department wanted to check if the customers are equally satisfied with the service provided at these two stores. A sample of 380 customers selected from Supermarket I produced a mean satisfaction index of 7.6 (on a scale of 1 to 10, 1 being the lowest and 10 being the highest) with a stan- dard deviation of .75. Another sample of 370 customers selected from Supermarket II produced a mean satisfaction index of 8.1 with a standard deviation of .59. Assume that the customer satisfaction index for each supermarket has an unknown and different population standard deviation. a. Construct a 98% confidence interval for the difference between the mean satisfaction indexes for all customers for the two supermarkets. b. Test at the 1% significance level whether the mean satisfaction indexes for all customers for the two supermarkets are different.

Answer 1

2 /2 = 2.32 )-(9.32一1 (0.75) (0.53)" 370 (7.6-8.1 38 O 0-5-C2-32 Co 04g2 = -0, 6142- -To -o. 38 58 -0 3858 -H42. 4.37834.3783 2-58 too Supermarket qre different