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标题: Prep-DS-126 [打印本页]

作者: hanxiao257 时间: 2010-6-2 14:17 标题: Prep-DS-126

126. 12631-!-item-!-187;#058&009380
9.4 9.9 9.9 9.9 10.0 10.2 10.2 10.5
The mean and the standard deviation of the 8 numbers shown are 10.0 and 0.3, respectively. What percent of the 8 numbers are within 1 standard deviation of the mean?

(A) 90%
(B) 85%
(C) 80%
(D) 75%
(E) 70%

作者: pansy 时间: 2010-6-2 14:20

1 standard deviation of the mean
表示  10-0.3<number<10+0.3
9.7＜9.9  9.9  9.9  10.0  10.2  10.2＜10.3
有六个数在之中9.7和10.3之间,  6/8=75%

作者: hanxiao257 时间: 2010-6-2 16:14

回复 2# pansy

感谢感谢

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