PP2-PS-44

Kath1985

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

---------------------------------------------------------------------------------------------------------------------------

【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

再頂...

iamyaoyao

问的就是准确的数吧（exactly)所以直接13.5-2*1.5=10.5