77 7 P1=P{Y=y1} 153010 P2=P{Y=y2}=P2 7113 301510 把这些数据补充到前面表上 0 pi 7/15 7/30 7/10 0 7/30 1/15 3/10 7/10 3/10 p10 3 15 1 30 7 { } 10 7 30 7 15 7 { } 2 1 2 2 2 2 1 1 1 1 = = = = + = = = = = + =   =  =  i i i i p P Y y p p P Y y p Y X 0 1 pi. 0 7/15 7/30 7/10 1 7/30 1/15 3/10 p.j 7/10 3/10 1 把这些数据补充到前面表上: