请牛牛们帮我解答，prep1-106数学

lezifanwen

106  If a certain sample fo data has a mean of 20.0and a standard deviation of 3.0, which of the following values is more 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

请牛牛们帮我解答，谢谢了！

mymengming

你给的题目有问题啊，

    

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

意思是问哪个是在2个半标准差外的，20+/-2.5×3
只有12符合

lezifanwen

太感谢牛牛了！