问题如下:
According to the above table, what is the correlation of X and Y, given the joint probability table above?
选项:
A. -0.98.
B. 0.16.
C. 0.98.
解释:
A is correct
,
Cov(X,Y)=-4.8, standard deviations of X and Y are 1.90 and 2.58, as calculated before,
thus correlation of X and Y is -0.98
什么时候用/N求方差,什么时候用全概率公式要乘每种概率的方式求方差,有明确的规律和标志吗