Take the 2-minute tour ×
Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. It's 100% free, no registration required.

Per image below, how does A transform into B? I'm referring to specifically, how Px,y(x,z-x) turns into px(x)py(z-x) Thanks a lot for looking over my newbie question!

enter image description here

share|improve this question

1 Answer 1

up vote 1 down vote accepted

The problem statement is incomplete. The problem should have specified as an assumption that $X$ and $Y$ are independent. For independent random variables $X$ and $Y$, we have $$\Pr((X,Y)=(a,b))=\Pr(X=a)\Pr(Y=b).$$ That is what is being used to get from A to B.

share|improve this answer
    
thanks a lot!!! –  user1486802 Dec 1 '12 at 23:02

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.