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Math Help - Need some clarification on a formula

  1. #1
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    Need some clarification on a formula



    In the discrete case, is the summing notation used here interpreted such that I have to sum with regard to the sample space of Y, and then sum the result of that with respect to the sample space of X? Or do I consider both sample spaces and just sum once? The former sounds like a lot of work.

    Thanks!
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  2. #2
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    Re: Need some clarification on a formula

    The sum is ultimately over the set of pairs \{(x,y)\mid x\in S_X,y\in S_Y\}. You can imagine this set as a matrix. It does not matter whether you sum it rows first or columns first; you have to compute g(x,y)p_{XY}(x,y) for each pair (x,y) and then add them all together.
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  3. #3
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    Re: Need some clarification on a formula

    I see, thanks.
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