单选题 Regardless of the shape of a distribution, according to Chebyshev's Inequality, what is the minimum percentage of observations that will lie within + or - two standard deviations of the mean?

A、

A. 68%.
B、

B. 34%.
C、

C. 75%.

【正确答案】 C

【答案解析】
According to Chebyshev's Inequality, for any distribution, the minimum percentage of observations that lie within k standard deviations of the distribution mean is equal to: 1-(1/k²), with k equal to the number of standard deviations. If k=2, then the percentage of distributions is equal to 1-(1/4)=75%.