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Math Help - Simplify Var and Expected value?

  1. #1
    Newbie
    Joined
    Sep 2011
    Posts
    15

    Simplify Var and Expected value?

    Suppose E(X) = 5 and Var(X) = 3.
    FIND:
    a) Var(2x+4)
    ___________MY ATTEMPT_____________

    I used this formula from Wikipedia.
    Var(ax+b) = Var(ax) = a^2Var(x)

    Therefore,
    2^2 Var(x) = 4*3 = 12
    __________________________________

    Someone told me the answer is 10, I dont know why.

    Any tips

    Thanks
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  2. #2
    Grand Panjandrum
    Joined
    Nov 2005
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    someplace
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    Thanks
    4

    Re: Simplify Var and Expected value?

    Quote Originally Posted by blackZ View Post
    Suppose E(X) = 5 and Var(X) = 3.
    FIND:
    a) Var(2x+4)
    ___________MY ATTEMPT_____________

    I used this formula from Wikipedia.
    Var(ax+b) = Var(ax) = a^2Var(x)

    Therefore,
    2^2 Var(x) = 4*3 = 12
    __________________________________

    Someone told me the answer is 10, I dont know why.

    Any tips

    Thanks
    12 is right.

    CB
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