Expected Value and Variance?

Let X1, X2…..X10 be such that E(Xi) = 2/3 for all i, Var(Xi) = 2/9 for all i, and Cov(Xi,Xj)=-1/63 for all i and j with i=/=j. Let X=X1+ X2+…….+X10.
Find E(X) and Var(X).

I have no idea how to begin.


Thanks

Quote:

---

Originally Posted by blackZ

Let X1, X2…..X10 be such that E(Xi) = 2/3 for all i, Var(Xi) = 2/9 for all i, and Cov(Xi,Xj)=-1/63 for all i and j with i=/=j. Let X=X1+ X2+…….+X10.
Find E(X) and Var(X).

I have no idea how to begin.


Thanks

---

Start by going to the formulas you will have been given in your class notes and textbook and applying them. Show all your work, say exactly where you are stuck.