# Math Help - Joint Probability question

1. ## 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

2. 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.

3. 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.

4. 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).