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 than2.5 standard deviations from the mean?
(A) 12.0
(B) 13.5
(C) 17.0
(D) 23.5
(E) 26.5
--------------------------------------------------------------------------------------------------------------------------------- 【答案】 A
我想问values is more than2.5 standard deviations from the mean 这句话是啥意思， 作者: sunflower88 时间: 2011-5-2 20:45
ONE standard deviation from the mean: within 3 of the mean 平均值加减一倍方差
TWO ....: within 2*3 of the mean平均值加减两倍方差
2.5*3=7.5作者: season5924 时间: 2011-5-3 21:50
能解释一下LZ说的那句话什么意思么？
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