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发表于 2008-6-10 14:10:00 | 只看该作者

prep

110.   11364-!-item-!-187;#058&007646

The residents of Town X participated in a survey to determine the number of hours per week each resident spent watching television.  The distribution of the results of the survey had a mean of 21 hours and a standard deviation of 6 hours.  The number of hours that Pat, a resident of Town X, watched television last week was between 1 and 2 standard deviations below the mean.  Which of the following could be the number of hours that Pat watched television last week?

 

(A) 30

(B) 20

(C) 18

(D) 12

(E) 6

答案是D

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