00 E(X)=∑kFpg k=1 =Σkk-I)pg+∑pg =pq∑q)”+E(X)） y+ 2-卫 Tarx=瓦x]-[ExT=2-2 1q p  = − = 1 2 2 1 ( ) k k E X k pq    = −  = − = − + 1 1 1 1 ( 1) k k k k k k p q kpq ( ) ( ) 1 p q q E X k k =   +  = q p q pq 1 ) 1 (  + − = , 2 2 p − p = . 2 1 ( ) [ ] [ ( )] 2 2 2 2 2 p q p p p Var X E X E X − = − = − =