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标题: prep-110 [打印本页]

作者: rock19840717 时间: 2008-9-1 21:21
标题: prep-110

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

(D) 12

(E) 6

请教做题思路，谢谢啦

作者: rorochen 时间: 2008-9-1 21:33

between 1 and 2 standard deviations below the mean. --〉X低于平均值，大概低1个标准差到2个标准差之间

(21-x)=6 --- 1个标准差

x=15

(21-x)=12 ---- 2个标准差

X=9

9-15之间

作者: rock19840717 时间: 2008-9-1 21:45
恩，刚在总结里看到了，还是语法区的兄弟姐妹好啊，感动的想哭，JJ区那帮人就盯着JJ了，太势利了，谢谢MM

作者: ivyfeng 时间: 2009-9-23 16:39
PREP110的标题怎么？？

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