Consumer reports uses a 100-point customer satisfaction score to rate the nations major chain stores. assume that from the past experience with the satisfaction rating score, a population standard deviation of 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. a sample of 15 costco customer satisfaction scores follow:

95 90 83 64 95
98 80 83 82 93
86 80 94 75 62
(a) what is the sample mean customer satisfaction score for costco?
(b) what is the sample variance?
(c) what is the sample standard deviation?

(A) Mean = 84

(B) Variance = 118.714

(C) Standard deviation = 10.89

Step-by-step explanation:

Data provided:

number of observations, n = 15

sample of 15 costco customer satisfaction scores follow

X                           

95                   11                   121

90                   6                   36

83                   -1                   1

64                   -20                400

95                   11                   121

98                   14                  196

80                   -4                     16

83                   -1                       1

82                   -2                     4

93                   9                     81

86                   2                       4

80                   -4                     16

94                   10                     100

75                   -9                      81

62                   -22                   484

================================================

                   ∑X = 1260         ∑= 1662

Now,

(A) Mean =

or

Mean =    = 84

(B) Variance =

or

Variance =

or

Variance = 118.714

(C) Standard deviation = √Variance = √118.714 = 10.89

the answer is c)8

step-by-step explanaction:

percentage - 25%

probability - 0.25

we know,

total amount of students in class = 20

total boys = 10

total girls = 10

no of girls who wear glasses = 10/2 = 5

probability of choosing a girl with glasses is =

number of girls wearing glasses/total number of students in the class = 5/20

thus, percentage of selecting a girl wearing glasses will be

= 5/20 × 100

= 5 × 5

25%

therefore,

probability will be 0.25

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