Joint Probability question

• Jul 27th 2010, 05:01 AM
neild
Joint Probability question
Hi,

I'm really struggling knowing where to get started with this question...

I can't find anything anywhere telling me how to go about it so any help would be very very much appreciated!

Thanks
• Jul 27th 2010, 06:29 AM
mr fantastic
Quote:

Originally Posted by neild
Hi,

I'm really struggling knowing where to get started with this question...

I can't find anything anywhere telling me how to go about it so any help would be very very much appreciated!

Thanks

Here's a foot in the door:

(a) $f(y, x) = f(y | x) \cdot f(x) = 8yx$ for $0 < y < x < 1$ and zero otherwise.
• Jul 28th 2010, 08:06 AM
neild
Okay, I understand part a) now but after a day of trying, cannot for the life of me understand how to do the rest.

Do I have to integrate to get a cumulative distribution function? And even then, I still don't understand how I can get it in just terms of Y for part b), and what I'm supposed to do for parts c) and d).

Sorry if I'm being stupid, but I really cannot understand what I'm doing at all. (Headbang)(Headbang)
• Jul 28th 2010, 05:11 PM
matheagle
You can integrate OUT the rv X to obtain the density of just Y
THEN integrate that from 0 to .5 to answer part (b).