NO.PZ2015120604000052
问题如下：
The table below shows part of the monthly stock returns of Ivy Corp.
Calculate the sample standard deviation for Ivy Corp. returns, assuming above tabe includes all samples??
选项：
A.8.78%.
B.8.01%.
C.77.1%2.
解释：
A is correct
Sample standard devation is 8.78%, the square root of sample variance 77.1%2
老师，我计算器输入之后，SX是0.087788，与选项一致，但是 方差是0.080139，X拔是0.076667也是对的，为啥方差不是C选项，标准差的平方呢？
