Question

For two random variables X and Y, if E(X)=5, E(X^2)=28, E(Y)=6, E(Y^2)=40, E(XY)=24. What is the value of Var(2X-Y)?

Answer 1

\(Var(2X-Y)=2^2Var(X)+Var(Y)+2(-2)Cov(X,Y)\)

\(Var(X)=E(X^2)=[E(X)]^2\)
\(Cov(X,Y)=E(XY)-E(X)E(Y)\)

Answer 2

\(Var(X)=E(X^2)-[E(X)]^2\) ** sorry

Answer 3

Thank you!

Answer 4

=] yw