If XXX and YYY are random variables such that Var(X+Y)=Var(X−Y)Var(X+Y) = Var(X-Y)Var(X+Y)=Var(X−Y), what must be true?
XXX and YYY are independent
Var(X)=Var(Y)Var(X) = Var(Y)Var(X)=Var(Y)
Cov(X,Y)=0Cov(X, Y) = 0Cov(X,Y)=0
X=YX = YX=Y almost surely