Showing the sum of binomial independent variables follows a binomial distribution using moment generating...












2














So I'm trying to solve the following problem:



Show that if $X_i$ follows a binomial distribution with $n_i$ trials, and probability of $p_i=p$ for $i = 1,2,3...n$, and the $X_i$ are independent, then $sum_{i=1}^{n}{X_i}$ follows a binomial distribution using moment generating functions.



Here's what I've tried so far:



$M_{sum_{i=1}^{n}}(t) = prod_{i=0}^{n}M_{X_i}(t) = prod_{i=0}^{n}(pe^t + 1 -p)^{n_i}$



I'm not sure where to go from here, or if I've even done everything correctly until this point. Any help will be greatly appreciated. Thanks!










share|cite|improve this question



























    2














    So I'm trying to solve the following problem:



    Show that if $X_i$ follows a binomial distribution with $n_i$ trials, and probability of $p_i=p$ for $i = 1,2,3...n$, and the $X_i$ are independent, then $sum_{i=1}^{n}{X_i}$ follows a binomial distribution using moment generating functions.



    Here's what I've tried so far:



    $M_{sum_{i=1}^{n}}(t) = prod_{i=0}^{n}M_{X_i}(t) = prod_{i=0}^{n}(pe^t + 1 -p)^{n_i}$



    I'm not sure where to go from here, or if I've even done everything correctly until this point. Any help will be greatly appreciated. Thanks!










    share|cite|improve this question

























      2












      2








      2







      So I'm trying to solve the following problem:



      Show that if $X_i$ follows a binomial distribution with $n_i$ trials, and probability of $p_i=p$ for $i = 1,2,3...n$, and the $X_i$ are independent, then $sum_{i=1}^{n}{X_i}$ follows a binomial distribution using moment generating functions.



      Here's what I've tried so far:



      $M_{sum_{i=1}^{n}}(t) = prod_{i=0}^{n}M_{X_i}(t) = prod_{i=0}^{n}(pe^t + 1 -p)^{n_i}$



      I'm not sure where to go from here, or if I've even done everything correctly until this point. Any help will be greatly appreciated. Thanks!










      share|cite|improve this question













      So I'm trying to solve the following problem:



      Show that if $X_i$ follows a binomial distribution with $n_i$ trials, and probability of $p_i=p$ for $i = 1,2,3...n$, and the $X_i$ are independent, then $sum_{i=1}^{n}{X_i}$ follows a binomial distribution using moment generating functions.



      Here's what I've tried so far:



      $M_{sum_{i=1}^{n}}(t) = prod_{i=0}^{n}M_{X_i}(t) = prod_{i=0}^{n}(pe^t + 1 -p)^{n_i}$



      I'm not sure where to go from here, or if I've even done everything correctly until this point. Any help will be greatly appreciated. Thanks!







      probability probability-distributions binomial-distribution moment-generating-functions






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      share|cite|improve this question











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      share|cite|improve this question










      asked Dec 2 at 0:50









      BeepBoop

      1135




      1135






















          1 Answer
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          begin{align}
          M_{sum_{i=1}^{n}X_i}(t) &= prod_{i=1}^{n}M_{X_i}(t)\
          & = prod_{i=1}^{n}(pe^t + 1 -p)^{n_i}\
          &=(pe^t + 1 -p)^{sum_{i=1}^{n} n_i}
          end{align}






          share|cite|improve this answer























          • ah ok, but how is that a Bernoulli distribution?
            – BeepBoop
            Dec 2 at 3:13






          • 1




            Do you mean Binomial?
            – Thomas Shelby
            Dec 2 at 6:23










          • Recall the uniqueness of moment generating functions.
            – Thomas Shelby
            Dec 2 at 6:27











          Your Answer





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          1 Answer
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          begin{align}
          M_{sum_{i=1}^{n}X_i}(t) &= prod_{i=1}^{n}M_{X_i}(t)\
          & = prod_{i=1}^{n}(pe^t + 1 -p)^{n_i}\
          &=(pe^t + 1 -p)^{sum_{i=1}^{n} n_i}
          end{align}






          share|cite|improve this answer























          • ah ok, but how is that a Bernoulli distribution?
            – BeepBoop
            Dec 2 at 3:13






          • 1




            Do you mean Binomial?
            – Thomas Shelby
            Dec 2 at 6:23










          • Recall the uniqueness of moment generating functions.
            – Thomas Shelby
            Dec 2 at 6:27
















          1














          begin{align}
          M_{sum_{i=1}^{n}X_i}(t) &= prod_{i=1}^{n}M_{X_i}(t)\
          & = prod_{i=1}^{n}(pe^t + 1 -p)^{n_i}\
          &=(pe^t + 1 -p)^{sum_{i=1}^{n} n_i}
          end{align}






          share|cite|improve this answer























          • ah ok, but how is that a Bernoulli distribution?
            – BeepBoop
            Dec 2 at 3:13






          • 1




            Do you mean Binomial?
            – Thomas Shelby
            Dec 2 at 6:23










          • Recall the uniqueness of moment generating functions.
            – Thomas Shelby
            Dec 2 at 6:27














          1












          1








          1






          begin{align}
          M_{sum_{i=1}^{n}X_i}(t) &= prod_{i=1}^{n}M_{X_i}(t)\
          & = prod_{i=1}^{n}(pe^t + 1 -p)^{n_i}\
          &=(pe^t + 1 -p)^{sum_{i=1}^{n} n_i}
          end{align}






          share|cite|improve this answer














          begin{align}
          M_{sum_{i=1}^{n}X_i}(t) &= prod_{i=1}^{n}M_{X_i}(t)\
          & = prod_{i=1}^{n}(pe^t + 1 -p)^{n_i}\
          &=(pe^t + 1 -p)^{sum_{i=1}^{n} n_i}
          end{align}







          share|cite|improve this answer














          share|cite|improve this answer



          share|cite|improve this answer








          edited Dec 2 at 6:42

























          answered Dec 2 at 1:37









          Thomas Shelby

          1,358216




          1,358216












          • ah ok, but how is that a Bernoulli distribution?
            – BeepBoop
            Dec 2 at 3:13






          • 1




            Do you mean Binomial?
            – Thomas Shelby
            Dec 2 at 6:23










          • Recall the uniqueness of moment generating functions.
            – Thomas Shelby
            Dec 2 at 6:27


















          • ah ok, but how is that a Bernoulli distribution?
            – BeepBoop
            Dec 2 at 3:13






          • 1




            Do you mean Binomial?
            – Thomas Shelby
            Dec 2 at 6:23










          • Recall the uniqueness of moment generating functions.
            – Thomas Shelby
            Dec 2 at 6:27
















          ah ok, but how is that a Bernoulli distribution?
          – BeepBoop
          Dec 2 at 3:13




          ah ok, but how is that a Bernoulli distribution?
          – BeepBoop
          Dec 2 at 3:13




          1




          1




          Do you mean Binomial?
          – Thomas Shelby
          Dec 2 at 6:23




          Do you mean Binomial?
          – Thomas Shelby
          Dec 2 at 6:23












          Recall the uniqueness of moment generating functions.
          – Thomas Shelby
          Dec 2 at 6:27




          Recall the uniqueness of moment generating functions.
          – Thomas Shelby
          Dec 2 at 6:27


















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