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Find P(X>4Y) given joint pdf

  1. Apr 2, 2013 #1
    1. The problem statement, all variables and given/known data

    Suppose X and Y have the joint probability density function:

    f(x,y) = x+4y, 0<y<x<1
    f(x,y) = 0 otherwise

    Find P(X>4Y)

    2. Relevant equations

    3. The attempt at a solution

    I'm not sure how to do this. I've already found marginal pdf's for x and y.. although I don't know if they're relevant.

    p1(x) = 3x^2
    p2(y) = (-9/2)y^2+4y+(1/2)

    Thanks for the help
  2. jcsd
  3. Apr 2, 2013 #2


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    Homework Helper

    I agree with your values for the marginals. Although I don't think they are relevant for this question.. There may be a way to do it, making use of the marginals, but that is not the way I did it.

    You should start by writing an equation for P(X>4Y) using the equation f(x,y)
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