# Probability, show that

1. Feb 3, 2009

### MaxManus

1. The problem statement, all variables and given/known data
Consider two random variables X and Y. Suppose that Y takes on k values yi,....,yk and X takes l values xi,....,xl

Hey, I am supposed to show that
1) Pr(Y = yi = $$\sum$$,from 1 to l Pr(Y = yi(givrn)(X=xi)Pr(X=xi)

and
2) E(Y) = E(E(Y(given)X)

I am not sure where to start on neither of them,

2. Feb 6, 2009

### Tom Mattson

Staff Emeritus
You need to learn how to do a little research, bro. That second problem is worked out completely on a wikipedia page, which I was able to find in about 20 seconds. I will let you think about what keywords to search for (you should at least know what E(Y) is called). As for the first problem, I'm guessing that you didn't type it in correctly because I can't parse what you're trying to say. Try again?