问题如下:
According to the above table, what is the variance of X?
选项:
A.3.6.
B.1.90.
C.6.64.
解释:
A is correct
Firstly ,We calulate expected return of X, E(X) = (0.2)(-2) + (0.6)(1) + (0.2)(4) = 1,
Then,Var(X) = 0.2(-2-1)2 + 0.6(1-1)2 + 0.2(4-1)2 = 3.6
这个题与y有什么关系呀?
第一步的期望不知道怎么算