请教一道题

albertjerrys

the arithmetic mean and standard deviation of a certain normal distribution are 13.5 and 1.5,respectively,what value is exactly 2 standard deviations less than the mean?

10.5

11

11.5

12

12.5

偶竟然连题目都没看懂。。。

albertjerrys

谢谢哦~偶真是那个。。。啊

wenchongjie

一个正态分布均值与标准差分别为13.5,1.5;问哪个数字比均值正好小2个标准差？

13.5-2*1.5=10.5