# Joint PDFs

• Jun 1st 2010, 05:19 AM
lh1188
Joint PDFs
Hi
I am really stuck on how to work out this maths problem. Could someone give me a bit of guidance on how to get it started.

Let f(x1, x2) = 4x1x2, 0 < x1 < 1, 0 < x2 < 1,
= 0 elsewhere.
I need to find this below

P(x1 = x2)

Thank you
• Jun 1st 2010, 05:32 AM
mr fantastic
Quote:

Originally Posted by lh1188
Hi
I am really stuck on how to work out this maths problem. Could someone give me a bit of guidance on how to get it started.

Let f(x1, x2) = 4x1x2, 0 < x1 < 1, 0 < x2 < 1,
= 0 elsewhere.
I need to find this below

P(x1 = x2)

Thank you

Are you sure the question wasn't something like find Pr(x1 < x2) ....?
• Jun 1st 2010, 05:52 AM
lh1188
That was the next question that we were given.

I have the answer to the question so I knew it was 0 but I do not know why.
For some reason we have limited information regarding this in our notes and as I have very limited statistical knowledge it is proving rather difficult to work out.
If you could give me a bit of guidance it would be very appreciated as I have an economics exam tomorrow!
• Jun 1st 2010, 05:58 AM
mr fantastic
Quote:

Originally Posted by lh1188
That was the next question that we were given.

I have the answer to the question so I knew it was 0 but I do not know why.
For some reason we have limited information regarding this in our notes and as I have very limited statistical knowledge it is proving rather difficult to work out.
If you could give me a bit of guidance it would be very appreciated as I have an economics exam tomorrow!

Pr(X = a) = 0 for any continuous random variable .... (such will be somewhere in your classnotes and textbook).
• Jun 1st 2010, 06:02 AM
lh1188