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Thread: quick question about notation in the definition of E(X)

  1. January 22nd 2011, 11:49 PM #1
    Volga
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    quick question about notation in the definition of E(X)

    What is the meaning of the subscript x at the bottom of the summation sign in the definition of the mean of the discrete random variable?

    E(X)=\Sigma_xxf_X(x)

    I am used to seeing the summation sign with the 'starting' point for summation at the bottom and the 'ending' at the top. I guess x here is 'x belongs to whatever interval is relevant for the distribution you are dealing with'? (eg binomial from x=1,2, ...n etc?)
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  2. January 23rd 2011, 12:07 AM #2
    FernandoRevilla
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    x\in \textrm{range}X


    Fernando Revilla
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