Q2:D

A certain characteristic in a large population has a distribution that is symmetric about the mean m.  If 68 percent of the distribution lies within one standard deviation d of the mean, what percent of the distribution is less than m + d ?

A.     16%

B.     32%

C.     48%

D.     84%

E.      92%

这题答案是D，我花了15分钟都没做出来，哪位好心给讲讲。。。

其实m+d就是一d为中心左右为-m和+m的分布。那么m+d就是分布在d的右边。

也就是68%+1/2（100%-68%）=84%