GWD18-18

meckychen

Q18:

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%
Answer is D. how to calculate? 3X

大荣

(m-d, m+d)占68%，剩下的占32%。由对称可知，大于m+d占16%。所以小于m+d的占84%。