NO.PZ2018062001000005
问题如下：
When determining the relative degree of variability of different data sets if those data sets have different means or different units of measurement, which of the following parameters is most suitable parameter?
选项：
A.Coefficient of variation.
B.Standard deviation.
C.Mean.
解释：
The relative measurement of risk is the coefficient of variation, which is more useful for measuring data sets with different mean and data sets with different unit of measurement than standard deviation or mean.
数值不同，平均不同的时候表示离散程度为什么不能用标准差呢？cv不就是比标准差更加精准表现离散程度么？但是在这道题里标准差不就够了么？
