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Math Help - finding the standard deviation of the variable????

  1. #1
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    finding the standard deviation of the variable????

    can anybody help solve this please
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  2. #2
    Moo
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    Hello,
    Quote Originally Posted by arslan View Post
    can anybody help solve this please
    For any rv X and Y, \mathbb{E}(X+Y)=\mathbb{E}(X)+\mathbb{E}(Y)

    For any independent rv X and Y, \text{Var}(X+Y)=\text{Var}(X)+\text{Var}(Y)
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  3. #3
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    Quote Originally Posted by Moo View Post
    Hello,

    For any rv X and Y, \mathbb{E}(X+Y)=\mathbb{E}(X)+\mathbb{E}(Y)

    For any independent rv X and Y, \text{Var}(X+Y)=\text{Var}(X)+\text{Var}(Y)
    how???
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  4. #4
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    Quote Originally Posted by arslan View Post
    how???
    E(X + Y) = E(X) + E(Y) is easily proved from the definition of expected value.

    For the proof of Var(X + Y) = Var(X) + Var(Y), read this: Variance of the Sum of Two Independent Random Variables
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