作者filley (我要改变...)
看板GMAT
标题[计量] PP标准差题目
时间Thu Nov 27 16:31:19 2008
106. 11122-!-item-!-187;#058&007588
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
答案是A
这种题目要怎麽解呢??
该不会要代标准差公式吧XD
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