→ yhliu :Cov(A,B) = Cov(X+Y,X-Y) = Var(X)-Var(Y) = 2^2-3^2 06/29 19:08
→ yhliu :Var(A) = Var(X+Y) = Var(X)+Var(Y)+2Cov(X,Y) 06/29 19:09
→ yhliu :Var(B) = Var(X-Y) = Var(X)+Var(Y)-2Cov(X,Y) 06/29 19:10
→ yhliu :因 Corr(X,Y) = 0, 故 Cov(X,Y) = 0, 所以 06/29 19:11
→ yhliu :Var(A) = Var(Y) = 2^2+3^2 = 13 06/29 19:11
→ yhliu :Corr(A,B) = Cov(A,B)/√[Var(A)Var(B)] = -5/13 06/29 19:12