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Math Help - Covariance

  1. #1
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    Covariance

    Let
    X be a random variable taking the values 1 and 2 with equal probability. Let Y = X^2.

    How do i calculate the Cov(X,Y)?
    i'm not sure which formula to use because ive tried Cov(X,Y) = E(XY)-(E(X)E(Y))
    but that equals 0

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  2. #2
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    i think i might of figured this one out the covariance is 0 because the random variables are independent?
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  3. #3
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    Quote Originally Posted by dexza666 View Post
    i think i might of figured this one out the covariance is 0 because the random variables are independent?
    Yes !

    \text{X and Y are independent } \Longleftrightarrow \text{ cov}(X,Y)=0


    But here, I'm not sure they're independent... you gotta prove it !
    Last edited by Moo; September 5th 2008 at 11:38 PM.
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