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Thread: Joint PDF problem

  1. #16
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    Re: Joint PDF problem




    Quote Originally Posted by _joey View Post
    because it is a property of a joint distribution function. And either way you integrate it should be equal to 1. You are still not sure?
    you obviously don't know what you are talking about.

    Just to end this quickly...if you want to integrate x then y you can do this...


    \int\limits_{0}^{1}\int\limits_{0}^{y}6x^2ydxdy+\int\limits_{1}^{2}\int\limits_{0}^{2-y}6x^2ydxdy=1


    though I already showed that it integrated to 1 so this is just a waste of time.
    Dr. Zoidberg: Fry, it's been years since medical school, so remind me. Disemboweling in your species, fatal or non-fatal?

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    Re: Joint PDF problem

    What he is saying is that you can integrate it in either order but the limits of your integration might need to change to reflect that. If you have variables in your integration limits you can't just switch the order without changing things around.

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    Re: Joint PDF problem

    Quote Originally Posted by Martingale View Post
    S

    Edit: let me clarify since you didn't understand...Why should it be with those particular limits
    I don't understand? I think you didn't understand. I stated in my very first post, post number 6.

    http://talkstats.com/showpost.php?p=38964&postcount=6

    "Different bounds are needed. "

    It took you a while to realise this
    Why was I stating that this will not work with the bounds you provided when we integrate in different order? Because your solution is incomplete. Once again, remember the properties of a valid joint pdf.

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    Re: Joint PDF problem

    Quote Originally Posted by Martingale View Post
    you obviously don't know what you are talking about.
    Yes, I do


    \int\limits_{0}^{1}\int\limits_{0}^{y}6x^2ydxdy+\int\limits_{1}^{2}\int\limits_{0}^{2-y}6x^2ydxdy=1
    That's better! Much better


    though I already showed that it integrated to 1 so this is just a waste of time.
    It's not. The solution was not complete. But you now you have shown it in different order... So, problem solved.

  5. #20
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    Re: Joint PDF problem

    Quote Originally Posted by _joey View Post
    Yes, I do



    That's better! Much better




    It's not. The solution was not complete. But you now you have shown it in different order... So, problem solved.

    The solution was complete. f(x,y)>=0 and it integrated to 1. geesh
    Dr. Zoidberg: Fry, it's been years since medical school, so remind me. Disemboweling in your species, fatal or non-fatal?

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    Re: Joint PDF problem

    Quote Originally Posted by Martingale View Post
    The solution was complete. f(x,y)>=0 and it integrated to 1. geesh
    I wouldn't be giving you full marks if I was checking your work. But thanks for replies anyway

  7. #22
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    Re: Joint PDF problem


    Quote Originally Posted by _joey View Post
    I wouldn't be giving you full marks if I was checking your work. But thanks for replies anyway
    Again you clearly don't know what you are talking about. I'm also betting that you didn't even know how to switch the limits (even though it is a simple undergraduate problem)

    Anyway this discussion is over.
    Dr. Zoidberg: Fry, it's been years since medical school, so remind me. Disemboweling in your species, fatal or non-fatal?

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