[心得] 條件期望值 條件變異數!! 題目
因為老師都沒給這部份的練習
所以 我去找了題目 就順便給大家練習吧
Q:
f(x,y)= (x+2y)/18 , when (x,y)=(1,1), (1,2), (2,1), (2.2)
0 , for all other pairs of X,Y
(1) Find the marginal distribution f(x) and f(y)
(2) Find the conditional mean and variance of Y when X=1
Ans: f(x)= 8/18 X=1 f(x)= 10/18 X=2
f(y)= 7/18 Y=1 f(y)= 11/18 Y=2
E(Y 1 X=1)= 13/8 Var(Y 1 X=1)= 15/64
以上"清大經研"
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