EX=p,EY=P DX=pq,DY=pq E(XY)=P Cov(X,Y)=E(XY)-EXEY=pq =1 Cov(X,Y) PxY-DX DYDX pq DY pq EX p EY p = = = = , , E(XY ) = p 1 ( , ) ( , ) ( ) = = = − = DX DY Cov X Y Cov X Y E XY EXEY pq ρ XY