Simplification of Summation for an Expected Value Problem












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I am not good with series or summation notation. Could someone explain how they simplified the expression in this image. Thanks!










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    -1












    $begingroup$


    I am not good with series or summation notation. Could someone explain how they simplified the expression in this image. Thanks!










    share|cite|improve this question









    $endgroup$















      -1












      -1








      -1





      $begingroup$


      I am not good with series or summation notation. Could someone explain how they simplified the expression in this image. Thanks!










      share|cite|improve this question









      $endgroup$




      I am not good with series or summation notation. Could someone explain how they simplified the expression in this image. Thanks!







      summation random-variables expected-value






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      asked Dec 5 '18 at 23:19









      Raoul DukeRaoul Duke

      34




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          1 Answer
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          $begingroup$

          Since $k=0$ and $k=1$, the sum becomes



          $$sum_{k=0}^1sum_{ell = 0}^3 3(1+k)ell p_{X,Y}(k,ell) = sum_{ell = 0}^3 left[3 ell p_{X,Y}(0,ell) + 3(1+1)ell p_{X,Y}(1,ell)right]$$
          $$=$$
          $$sum_{ell = 0}^3 3ell p_{X,Y}(0,ell) + sum_{ell = 0}^36ell p_{X,Y}(1,ell)$$



          simply by using the fact that :



          $$sum(a+b) = sum a + sum b$$






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Thank you. I think the variables confused me
            $endgroup$
            – Raoul Duke
            Dec 5 '18 at 23:30










          • $begingroup$
            No problem, if you are a begginer, summations usually scare people away ! Glad I could help.
            $endgroup$
            – Rebellos
            Dec 5 '18 at 23:31










          • $begingroup$
            Is there a reason I got down-voted by someone? Not upset, just want to make sure I'm following the community guidelines correctly.
            $endgroup$
            – Raoul Duke
            Dec 6 '18 at 0:14













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          $begingroup$

          Since $k=0$ and $k=1$, the sum becomes



          $$sum_{k=0}^1sum_{ell = 0}^3 3(1+k)ell p_{X,Y}(k,ell) = sum_{ell = 0}^3 left[3 ell p_{X,Y}(0,ell) + 3(1+1)ell p_{X,Y}(1,ell)right]$$
          $$=$$
          $$sum_{ell = 0}^3 3ell p_{X,Y}(0,ell) + sum_{ell = 0}^36ell p_{X,Y}(1,ell)$$



          simply by using the fact that :



          $$sum(a+b) = sum a + sum b$$






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Thank you. I think the variables confused me
            $endgroup$
            – Raoul Duke
            Dec 5 '18 at 23:30










          • $begingroup$
            No problem, if you are a begginer, summations usually scare people away ! Glad I could help.
            $endgroup$
            – Rebellos
            Dec 5 '18 at 23:31










          • $begingroup$
            Is there a reason I got down-voted by someone? Not upset, just want to make sure I'm following the community guidelines correctly.
            $endgroup$
            – Raoul Duke
            Dec 6 '18 at 0:14


















          1












          $begingroup$

          Since $k=0$ and $k=1$, the sum becomes



          $$sum_{k=0}^1sum_{ell = 0}^3 3(1+k)ell p_{X,Y}(k,ell) = sum_{ell = 0}^3 left[3 ell p_{X,Y}(0,ell) + 3(1+1)ell p_{X,Y}(1,ell)right]$$
          $$=$$
          $$sum_{ell = 0}^3 3ell p_{X,Y}(0,ell) + sum_{ell = 0}^36ell p_{X,Y}(1,ell)$$



          simply by using the fact that :



          $$sum(a+b) = sum a + sum b$$






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Thank you. I think the variables confused me
            $endgroup$
            – Raoul Duke
            Dec 5 '18 at 23:30










          • $begingroup$
            No problem, if you are a begginer, summations usually scare people away ! Glad I could help.
            $endgroup$
            – Rebellos
            Dec 5 '18 at 23:31










          • $begingroup$
            Is there a reason I got down-voted by someone? Not upset, just want to make sure I'm following the community guidelines correctly.
            $endgroup$
            – Raoul Duke
            Dec 6 '18 at 0:14
















          1












          1








          1





          $begingroup$

          Since $k=0$ and $k=1$, the sum becomes



          $$sum_{k=0}^1sum_{ell = 0}^3 3(1+k)ell p_{X,Y}(k,ell) = sum_{ell = 0}^3 left[3 ell p_{X,Y}(0,ell) + 3(1+1)ell p_{X,Y}(1,ell)right]$$
          $$=$$
          $$sum_{ell = 0}^3 3ell p_{X,Y}(0,ell) + sum_{ell = 0}^36ell p_{X,Y}(1,ell)$$



          simply by using the fact that :



          $$sum(a+b) = sum a + sum b$$






          share|cite|improve this answer









          $endgroup$



          Since $k=0$ and $k=1$, the sum becomes



          $$sum_{k=0}^1sum_{ell = 0}^3 3(1+k)ell p_{X,Y}(k,ell) = sum_{ell = 0}^3 left[3 ell p_{X,Y}(0,ell) + 3(1+1)ell p_{X,Y}(1,ell)right]$$
          $$=$$
          $$sum_{ell = 0}^3 3ell p_{X,Y}(0,ell) + sum_{ell = 0}^36ell p_{X,Y}(1,ell)$$



          simply by using the fact that :



          $$sum(a+b) = sum a + sum b$$







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Dec 5 '18 at 23:25









          RebellosRebellos

          14.5k31246




          14.5k31246












          • $begingroup$
            Thank you. I think the variables confused me
            $endgroup$
            – Raoul Duke
            Dec 5 '18 at 23:30










          • $begingroup$
            No problem, if you are a begginer, summations usually scare people away ! Glad I could help.
            $endgroup$
            – Rebellos
            Dec 5 '18 at 23:31










          • $begingroup$
            Is there a reason I got down-voted by someone? Not upset, just want to make sure I'm following the community guidelines correctly.
            $endgroup$
            – Raoul Duke
            Dec 6 '18 at 0:14




















          • $begingroup$
            Thank you. I think the variables confused me
            $endgroup$
            – Raoul Duke
            Dec 5 '18 at 23:30










          • $begingroup$
            No problem, if you are a begginer, summations usually scare people away ! Glad I could help.
            $endgroup$
            – Rebellos
            Dec 5 '18 at 23:31










          • $begingroup$
            Is there a reason I got down-voted by someone? Not upset, just want to make sure I'm following the community guidelines correctly.
            $endgroup$
            – Raoul Duke
            Dec 6 '18 at 0:14


















          $begingroup$
          Thank you. I think the variables confused me
          $endgroup$
          – Raoul Duke
          Dec 5 '18 at 23:30




          $begingroup$
          Thank you. I think the variables confused me
          $endgroup$
          – Raoul Duke
          Dec 5 '18 at 23:30












          $begingroup$
          No problem, if you are a begginer, summations usually scare people away ! Glad I could help.
          $endgroup$
          – Rebellos
          Dec 5 '18 at 23:31




          $begingroup$
          No problem, if you are a begginer, summations usually scare people away ! Glad I could help.
          $endgroup$
          – Rebellos
          Dec 5 '18 at 23:31












          $begingroup$
          Is there a reason I got down-voted by someone? Not upset, just want to make sure I'm following the community guidelines correctly.
          $endgroup$
          – Raoul Duke
          Dec 6 '18 at 0:14






          $begingroup$
          Is there a reason I got down-voted by someone? Not upset, just want to make sure I'm following the community guidelines correctly.
          $endgroup$
          – Raoul Duke
          Dec 6 '18 at 0:14




















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