设二维随机变量(X,Y)的联合概率密度为 f(x,y)={cx^2y 0<x<1 0<y<1} 0 其他 求:(1)常数c; (2) P{X<0.5,Y<

2024-11-30 20:14:15
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回答1:

(1)F(X,Y)=f(0,1)f(01)cx^2ydydx=c/2f(0,1)x^2dx=c/6x^3(0,1)=c/6=1
c=6
(2)P{X<0.5,Y<0.5}=f(0,0.5)F(0,0.5)6x^2ydydx=f(0,1)3/4x^2dx=1/32
(3)fx(X)=f(0,1)6x^2ydy=3x^2
(4)E(X)=f(0,1)xfx(X)dx=f(0,1)3x^3dx=3/4
(5)cov(x,y)=E(XY)-E(X)E(Y)后面的敏如自己算含肆啊,有事要走开谈拿轿