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Thread: gamma distribution.

  1. March 6th 2010, 01:44 AM #1
    alexandrabel90
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    gamma distribution.

    using gamma random variable, how do you find the variance of L= 30Y + 2Y^2 given that alpha = 3 and beta = 2?

    may i know what is the formula for V(Y^2) and how do i work out the formula in terms of alpha and beta?
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  2. March 6th 2010, 07:11 AM #2
    matheagle
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    Use V(L)=E(L^2)-(E(L))^2

    E(L^2)=E((30Y+2Y^2)^2)=900E(Y^2)+120E(Y^3)+4E(Y^4)

    Likewise, find E(L)

    Use the MGF to obtain the moments of your gamma distribution.
    If you haven't learned that yet, you coudluse wikipedia,
    or use a thread here that found the k{th} moment for the gamma.
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