Ch4-91 E(X￥)=p,E(Y)=p, D(X)=p,D()=m, E(Xr=P, coV(X, Y=pq, P XYCh4-91 ( ) , ( ) , ( ) , ( ) , D X pq D Y pq E X p E Y p = = = = E(XY) = p, cov( X,Y) = pq,  XY =1