更新时间2019-03-12 01:08:59
如果(x,y)的联合分布律为
x/y 1 2
1 1/6 1/3
2 1/9 2/9
3 1/18 a
(1)a的值
(2)x和y的边际分布
(1)、a = 1/18 * ( 2/1 ) = 1/9;
(2)、边际分布
x/y 1 2 P( x = xi )
1 1/6 1/3 1/6+1/3 = 1/2
2 1/9 2/9 1/9+2/9 = 1/3
3 1/18 1/9 1/18+1/9 = 1/6
P( y = yi ) 1/6+1/9+1/18 = 1/3 1/3+2/9+1/9 = 2/3