Results 1 to 6 of 6

Math Help - Joint PDFs

  1. #1
    Newbie
    Joined
    Jun 2010
    Posts
    3

    Exclamation 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
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by lh1188 View Post
    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
    The answer is zero and you should think about why ....

    Are you sure the question wasn't something like find Pr(x1 < x2) ....?
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Jun 2010
    Posts
    3
    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!
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by lh1188 View Post
    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).
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    Jun 2010
    Posts
    3

    Thumbs up

    Thank you for your help!
    Follow Math Help Forum on Facebook and Google+

  6. #6
    MHF Contributor matheagle's Avatar
    Joined
    Feb 2009
    Posts
    2,763
    Thanks
    5
    also by inspection the two rvs are independent with densities
    2x1 and 2x2 on (0,1)
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. combining pdfs
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: October 18th 2010, 03:17 PM
  2. Replies: 5
    Last Post: December 5th 2009, 11:30 PM
  3. Limits when evaluating joint pdfs
    Posted in the Advanced Statistics Forum
    Replies: 8
    Last Post: August 16th 2009, 07:37 PM
  4. [SOLVED] joint pdfs
    Posted in the Advanced Statistics Forum
    Replies: 4
    Last Post: December 8th 2008, 12:27 AM
  5. Mean and Variance of joint marginal pdfs?
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: November 6th 2008, 12:26 AM

Search Tags


/mathhelpforum @mathhelpforum