[求助][讨论]Prep难题，几题统计

tekofrlo

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                                          7.51   8.22   7.86   8.36

                                          8.09   7.83   8.30   8.01

                                          7.73   8.25   7.96   8.53

121. A vending machine is designed to dispense 8 ounces of coffee into a cup. After a test that recorded the number of ounces of coffee in each of 1,000 cups dispensed by the vending machine, the 12 listed amounts, in ounces, were selected from the data. If the 1,000 recorded amounts have a mean of 8.1 ounces and a standard deviation of 0.3 ounce, how many of the 12 listed amounts are within 1.5 standard deviations of the mean?

(A) Four

(B) Six

(C) Nine

(D) Ten

(E) Eleven

E

118. For a certain examination, a score of 58 was 2 standard deviations below the mean, and a score of 98 was 3 standard deviations above the mean. What was the mean score for the examination?

(A) 74

(B) 76

(C) 78

(D) 80

(E) 82

A

106. If a certain sample of data has a mean of 20.0 and a standard deviation of 3.0, which of the following values is more than 2.5 standard deviations from the mean?

(A) 12.0

(B) 13.5

(C) 17.0

(D) 23.5

(E) 26.5

A