Question

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 a 14 is expected. In 2012. Costco, with its 432 warehouses in 40 states, was the only chain store to cam an outstanding rating for overall quality. A sample of 15 Costco customer satisfaction scores follows 95 908375 95 83 82 93 94 6462 (a) What is the sample mean customer satisfaction score for Costco? (b) What is the sample variancez (Round your answer to two decimal places) (c) What is the sample standard deviation (Round your answer to two decimal places.)

Answer 1

(a) Sample mean (*): XS 1260 = 84 i Sample mean = 84 | (6) sample Variance (s): - 2 ECx;-X) . 1662 = 118.4143 Samal isol Sample variance (s). 118.71 c) Sample standard deviation (s) : 1662 - 10.8956 - 10.8956 V nel 15- ) S= 10.90

calculations :

Create the following table.

data	data-mean	(data - mean)2
95	11	121
98	14	196
86	2	4
90	6	36
80	-4	16
80	-4	16
83	-1	1
83	-1	1
94	10	100
75	-9	81
82	-2	4
64	-20	400
95	11	121
93	9	81
62	-22	484

Find the sum of numbers in the last column to get.

∑(xi−X bar )²=1662