NO.PZ2015120604000167
问题如下：
For any distribution, what is the minimum percentage that will lie within ±2 standard deviations of the mean?
选项：
A.25%
B.50%
C.75%
解释：
C is correct.
1-1/k2=1-1/22=1-1/4=0.75=75%
不太明白题目问的东西？希望老师能解答一下？没看出为什么跟chebyshev有关
