PP2-PS-44

Kath1985 · 发表于 2010-4-15 19:37:58

44.5884-!-item-!-187;#058&004663

The arithmetic mean and standard deviation of a certain normal distribution are 13.5 and 1.5, respectively.
What value is exactly2 standard deviations less than the mean?

(A) 10.5

(B)11.0

(C)11.5

(D) 12.0

(E) 12.5

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【答案】A

五個答案都不對吧....
答案應該小於10.5才對呀因為題目說要小於兩個標準差算式應該為 x < 13.5- (2 * 1.5 ) ,得x <10.5
請問哪裡不對了呢

Kath1985 · 发表于 2010-4-20 16:19:14

再頂...

iamyaoyao · 发表于 2010-4-20 16:32:02

问的就是准确的数吧（exactly)所以直接13.5-2*1.5=10.5

PP2-PS-44

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