Help on Moment Generating Functions

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I have recently been given a set of practice problems for my probabilities course and I have no idea where to even start on this question.




The distribution of X = the number of toppings ordered by a randomly selected customer is given in the table below. It turns out that X is independent of the size of the pizza and the type of cheese and that each topping is equally popular as are the two cheese types.



P(X=x)



0 = 0.3



1 = 0.3



2 = 0.1



3 = 0.1



4 = 0.2



What is the mgf of X?




I am pretty sure this is a Binomial Distribution. So would I just put $[(1-θ) + θe^t]n$ as my answer?



Overall I am really confused on this topic and would like some help that isn't too discrete. Thank You!










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    I have recently been given a set of practice problems for my probabilities course and I have no idea where to even start on this question.




    The distribution of X = the number of toppings ordered by a randomly selected customer is given in the table below. It turns out that X is independent of the size of the pizza and the type of cheese and that each topping is equally popular as are the two cheese types.



    P(X=x)



    0 = 0.3



    1 = 0.3



    2 = 0.1



    3 = 0.1



    4 = 0.2



    What is the mgf of X?




    I am pretty sure this is a Binomial Distribution. So would I just put $[(1-θ) + θe^t]n$ as my answer?



    Overall I am really confused on this topic and would like some help that isn't too discrete. Thank You!










    share|cite|improve this question









    New contributor




    Dillon Hector is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
    Check out our Code of Conduct.





















      up vote
      1
      down vote

      favorite









      up vote
      1
      down vote

      favorite











      I have recently been given a set of practice problems for my probabilities course and I have no idea where to even start on this question.




      The distribution of X = the number of toppings ordered by a randomly selected customer is given in the table below. It turns out that X is independent of the size of the pizza and the type of cheese and that each topping is equally popular as are the two cheese types.



      P(X=x)



      0 = 0.3



      1 = 0.3



      2 = 0.1



      3 = 0.1



      4 = 0.2



      What is the mgf of X?




      I am pretty sure this is a Binomial Distribution. So would I just put $[(1-θ) + θe^t]n$ as my answer?



      Overall I am really confused on this topic and would like some help that isn't too discrete. Thank You!










      share|cite|improve this question









      New contributor




      Dillon Hector is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.











      I have recently been given a set of practice problems for my probabilities course and I have no idea where to even start on this question.




      The distribution of X = the number of toppings ordered by a randomly selected customer is given in the table below. It turns out that X is independent of the size of the pizza and the type of cheese and that each topping is equally popular as are the two cheese types.



      P(X=x)



      0 = 0.3



      1 = 0.3



      2 = 0.1



      3 = 0.1



      4 = 0.2



      What is the mgf of X?




      I am pretty sure this is a Binomial Distribution. So would I just put $[(1-θ) + θe^t]n$ as my answer?



      Overall I am really confused on this topic and would like some help that isn't too discrete. Thank You!







      mgf






      share|cite|improve this question









      New contributor




      Dillon Hector is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.











      share|cite|improve this question









      New contributor




      Dillon Hector is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.









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      share|cite|improve this question








      edited 1 hour ago









      SecretAgentMan

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      asked 2 hours ago









      Dillon Hector

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      New contributor





      Dillon Hector is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.






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      Check out our Code of Conduct.




















          1 Answer
          1






          active

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          up vote
          4
          down vote



          accepted










          $X$ is not a binomial distribution. A binomial distribution is the number of successes $X$ out of $n$ independent trials with constant probability of success $p$.



          Now to answer your question, you're given the PMF of your random variable $X$ explicitly. The moment generating function of a random variable $X$ is defined as



          $$M_X (t) = E[e^Xt]$$



          And for a discrete random variable $Z$, expectation of $g(Z)$ is defined as



          $E[g(Z)] = sum_z g(z) times P(Z=z)$



          Therefore, the moment generating function of your random variable $X$ is defined as



          $M_X(t) = sum_x e^xt times P(X=x) $



          $= e^0ttimes 0.3 + e^1ttimes 0.3 + e^2ttimes 0.1 + e^3ttimes 0.1 + e^4t times 0.2$



          Which is clearly a function in $t$ as you would expect






          share|cite|improve this answer










          New contributor




          Xiaomi is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
          Check out our Code of Conduct.

















          • So exactly what type of distribution would X be? If any.
            – Dillon Hector
            1 hour ago






          • 1




            It's not a specific type, it's described by the probability function given to you. So long as the function's probabilities sum to 1, it's a valid discrete distribution, it doesn't need to be of a specific type.
            – Xiaomi
            1 hour ago











          • Okay, so say I did get a Binomial Distribution, would I use the formula and then that is it? Or would I do what was done above? Sorry just a bit confused.
            – Dillon Hector
            1 hour ago










          • Yes. If you know $X$ has a Binomial$(n,p)$ distribution, then you can use the formula for it's MGF rather than deriving it. In the case of parameters $n,p$, it would have MGF $(1-p+pe^t)^n$. You just need to make sure the binomial assumptions are actually true, or if you are explitly told in the question. No need to apologize, you're here to learn after all!
            – Xiaomi
            1 hour ago










          • To further add: if you are explicitly told in the question "$X$ has ___ distribution with parameters ___" then you can just look up the distribution's wikipedia page and find it's MGF formula on the side bar. As long as you know the parameters, you can just chuck them in to the MGF formular right away
            – Xiaomi
            1 hour ago










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          1 Answer
          1






          active

          oldest

          votes








          1 Answer
          1






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes








          up vote
          4
          down vote



          accepted










          $X$ is not a binomial distribution. A binomial distribution is the number of successes $X$ out of $n$ independent trials with constant probability of success $p$.



          Now to answer your question, you're given the PMF of your random variable $X$ explicitly. The moment generating function of a random variable $X$ is defined as



          $$M_X (t) = E[e^Xt]$$



          And for a discrete random variable $Z$, expectation of $g(Z)$ is defined as



          $E[g(Z)] = sum_z g(z) times P(Z=z)$



          Therefore, the moment generating function of your random variable $X$ is defined as



          $M_X(t) = sum_x e^xt times P(X=x) $



          $= e^0ttimes 0.3 + e^1ttimes 0.3 + e^2ttimes 0.1 + e^3ttimes 0.1 + e^4t times 0.2$



          Which is clearly a function in $t$ as you would expect






          share|cite|improve this answer










          New contributor




          Xiaomi is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
          Check out our Code of Conduct.

















          • So exactly what type of distribution would X be? If any.
            – Dillon Hector
            1 hour ago






          • 1




            It's not a specific type, it's described by the probability function given to you. So long as the function's probabilities sum to 1, it's a valid discrete distribution, it doesn't need to be of a specific type.
            – Xiaomi
            1 hour ago











          • Okay, so say I did get a Binomial Distribution, would I use the formula and then that is it? Or would I do what was done above? Sorry just a bit confused.
            – Dillon Hector
            1 hour ago










          • Yes. If you know $X$ has a Binomial$(n,p)$ distribution, then you can use the formula for it's MGF rather than deriving it. In the case of parameters $n,p$, it would have MGF $(1-p+pe^t)^n$. You just need to make sure the binomial assumptions are actually true, or if you are explitly told in the question. No need to apologize, you're here to learn after all!
            – Xiaomi
            1 hour ago










          • To further add: if you are explicitly told in the question "$X$ has ___ distribution with parameters ___" then you can just look up the distribution's wikipedia page and find it's MGF formula on the side bar. As long as you know the parameters, you can just chuck them in to the MGF formular right away
            – Xiaomi
            1 hour ago














          up vote
          4
          down vote



          accepted










          $X$ is not a binomial distribution. A binomial distribution is the number of successes $X$ out of $n$ independent trials with constant probability of success $p$.



          Now to answer your question, you're given the PMF of your random variable $X$ explicitly. The moment generating function of a random variable $X$ is defined as



          $$M_X (t) = E[e^Xt]$$



          And for a discrete random variable $Z$, expectation of $g(Z)$ is defined as



          $E[g(Z)] = sum_z g(z) times P(Z=z)$



          Therefore, the moment generating function of your random variable $X$ is defined as



          $M_X(t) = sum_x e^xt times P(X=x) $



          $= e^0ttimes 0.3 + e^1ttimes 0.3 + e^2ttimes 0.1 + e^3ttimes 0.1 + e^4t times 0.2$



          Which is clearly a function in $t$ as you would expect






          share|cite|improve this answer










          New contributor




          Xiaomi is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
          Check out our Code of Conduct.

















          • So exactly what type of distribution would X be? If any.
            – Dillon Hector
            1 hour ago






          • 1




            It's not a specific type, it's described by the probability function given to you. So long as the function's probabilities sum to 1, it's a valid discrete distribution, it doesn't need to be of a specific type.
            – Xiaomi
            1 hour ago











          • Okay, so say I did get a Binomial Distribution, would I use the formula and then that is it? Or would I do what was done above? Sorry just a bit confused.
            – Dillon Hector
            1 hour ago










          • Yes. If you know $X$ has a Binomial$(n,p)$ distribution, then you can use the formula for it's MGF rather than deriving it. In the case of parameters $n,p$, it would have MGF $(1-p+pe^t)^n$. You just need to make sure the binomial assumptions are actually true, or if you are explitly told in the question. No need to apologize, you're here to learn after all!
            – Xiaomi
            1 hour ago










          • To further add: if you are explicitly told in the question "$X$ has ___ distribution with parameters ___" then you can just look up the distribution's wikipedia page and find it's MGF formula on the side bar. As long as you know the parameters, you can just chuck them in to the MGF formular right away
            – Xiaomi
            1 hour ago












          up vote
          4
          down vote



          accepted







          up vote
          4
          down vote



          accepted






          $X$ is not a binomial distribution. A binomial distribution is the number of successes $X$ out of $n$ independent trials with constant probability of success $p$.



          Now to answer your question, you're given the PMF of your random variable $X$ explicitly. The moment generating function of a random variable $X$ is defined as



          $$M_X (t) = E[e^Xt]$$



          And for a discrete random variable $Z$, expectation of $g(Z)$ is defined as



          $E[g(Z)] = sum_z g(z) times P(Z=z)$



          Therefore, the moment generating function of your random variable $X$ is defined as



          $M_X(t) = sum_x e^xt times P(X=x) $



          $= e^0ttimes 0.3 + e^1ttimes 0.3 + e^2ttimes 0.1 + e^3ttimes 0.1 + e^4t times 0.2$



          Which is clearly a function in $t$ as you would expect






          share|cite|improve this answer










          New contributor




          Xiaomi is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
          Check out our Code of Conduct.









          $X$ is not a binomial distribution. A binomial distribution is the number of successes $X$ out of $n$ independent trials with constant probability of success $p$.



          Now to answer your question, you're given the PMF of your random variable $X$ explicitly. The moment generating function of a random variable $X$ is defined as



          $$M_X (t) = E[e^Xt]$$



          And for a discrete random variable $Z$, expectation of $g(Z)$ is defined as



          $E[g(Z)] = sum_z g(z) times P(Z=z)$



          Therefore, the moment generating function of your random variable $X$ is defined as



          $M_X(t) = sum_x e^xt times P(X=x) $



          $= e^0ttimes 0.3 + e^1ttimes 0.3 + e^2ttimes 0.1 + e^3ttimes 0.1 + e^4t times 0.2$



          Which is clearly a function in $t$ as you would expect







          share|cite|improve this answer










          New contributor




          Xiaomi is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
          Check out our Code of Conduct.









          share|cite|improve this answer



          share|cite|improve this answer








          edited 3 mins ago





















          New contributor




          Xiaomi is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
          Check out our Code of Conduct.









          answered 1 hour ago









          Xiaomi

          905




          905




          New contributor




          Xiaomi is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
          Check out our Code of Conduct.





          New contributor





          Xiaomi is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
          Check out our Code of Conduct.






          Xiaomi is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
          Check out our Code of Conduct.











          • So exactly what type of distribution would X be? If any.
            – Dillon Hector
            1 hour ago






          • 1




            It's not a specific type, it's described by the probability function given to you. So long as the function's probabilities sum to 1, it's a valid discrete distribution, it doesn't need to be of a specific type.
            – Xiaomi
            1 hour ago











          • Okay, so say I did get a Binomial Distribution, would I use the formula and then that is it? Or would I do what was done above? Sorry just a bit confused.
            – Dillon Hector
            1 hour ago










          • Yes. If you know $X$ has a Binomial$(n,p)$ distribution, then you can use the formula for it's MGF rather than deriving it. In the case of parameters $n,p$, it would have MGF $(1-p+pe^t)^n$. You just need to make sure the binomial assumptions are actually true, or if you are explitly told in the question. No need to apologize, you're here to learn after all!
            – Xiaomi
            1 hour ago










          • To further add: if you are explicitly told in the question "$X$ has ___ distribution with parameters ___" then you can just look up the distribution's wikipedia page and find it's MGF formula on the side bar. As long as you know the parameters, you can just chuck them in to the MGF formular right away
            – Xiaomi
            1 hour ago
















          • So exactly what type of distribution would X be? If any.
            – Dillon Hector
            1 hour ago






          • 1




            It's not a specific type, it's described by the probability function given to you. So long as the function's probabilities sum to 1, it's a valid discrete distribution, it doesn't need to be of a specific type.
            – Xiaomi
            1 hour ago











          • Okay, so say I did get a Binomial Distribution, would I use the formula and then that is it? Or would I do what was done above? Sorry just a bit confused.
            – Dillon Hector
            1 hour ago










          • Yes. If you know $X$ has a Binomial$(n,p)$ distribution, then you can use the formula for it's MGF rather than deriving it. In the case of parameters $n,p$, it would have MGF $(1-p+pe^t)^n$. You just need to make sure the binomial assumptions are actually true, or if you are explitly told in the question. No need to apologize, you're here to learn after all!
            – Xiaomi
            1 hour ago










          • To further add: if you are explicitly told in the question "$X$ has ___ distribution with parameters ___" then you can just look up the distribution's wikipedia page and find it's MGF formula on the side bar. As long as you know the parameters, you can just chuck them in to the MGF formular right away
            – Xiaomi
            1 hour ago















          So exactly what type of distribution would X be? If any.
          – Dillon Hector
          1 hour ago




          So exactly what type of distribution would X be? If any.
          – Dillon Hector
          1 hour ago




          1




          1




          It's not a specific type, it's described by the probability function given to you. So long as the function's probabilities sum to 1, it's a valid discrete distribution, it doesn't need to be of a specific type.
          – Xiaomi
          1 hour ago





          It's not a specific type, it's described by the probability function given to you. So long as the function's probabilities sum to 1, it's a valid discrete distribution, it doesn't need to be of a specific type.
          – Xiaomi
          1 hour ago













          Okay, so say I did get a Binomial Distribution, would I use the formula and then that is it? Or would I do what was done above? Sorry just a bit confused.
          – Dillon Hector
          1 hour ago




          Okay, so say I did get a Binomial Distribution, would I use the formula and then that is it? Or would I do what was done above? Sorry just a bit confused.
          – Dillon Hector
          1 hour ago












          Yes. If you know $X$ has a Binomial$(n,p)$ distribution, then you can use the formula for it's MGF rather than deriving it. In the case of parameters $n,p$, it would have MGF $(1-p+pe^t)^n$. You just need to make sure the binomial assumptions are actually true, or if you are explitly told in the question. No need to apologize, you're here to learn after all!
          – Xiaomi
          1 hour ago




          Yes. If you know $X$ has a Binomial$(n,p)$ distribution, then you can use the formula for it's MGF rather than deriving it. In the case of parameters $n,p$, it would have MGF $(1-p+pe^t)^n$. You just need to make sure the binomial assumptions are actually true, or if you are explitly told in the question. No need to apologize, you're here to learn after all!
          – Xiaomi
          1 hour ago












          To further add: if you are explicitly told in the question "$X$ has ___ distribution with parameters ___" then you can just look up the distribution's wikipedia page and find it's MGF formula on the side bar. As long as you know the parameters, you can just chuck them in to the MGF formular right away
          – Xiaomi
          1 hour ago




          To further add: if you are explicitly told in the question "$X$ has ___ distribution with parameters ___" then you can just look up the distribution's wikipedia page and find it's MGF formula on the side bar. As long as you know the parameters, you can just chuck them in to the MGF formular right away
          – Xiaomi
          1 hour ago










          Dillon Hector is a new contributor. Be nice, and check out our Code of Conduct.









           

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