For a certain distribution,the measurement 12.1 is 1.5 standard deviations below the mean,and the me

题目

For a certain distribution,the measurement 12.1 is 1.5 standard deviations below the mean,and the measurement 17.5 is 3.0 standard deviations above the mean.What is the mean of the distribution?
A) 13.8 B) 13.9 C)14.0 D) 14.1 E) 14.2

答案

这题目的意思是某一个平均数的1.5标准偏差下限是12.5,3标准偏差上限是17.5；
设平均值为x,标准偏差为s
x-1.5s=12.1
x+3s=17.5
解得x=13.9
所以选 B