Characteristic function of independent Poisson random variables












1












$begingroup$


Let $X_{i}$ be independent Poisson distributed random variables with parameter $lambda_{i} > 0$ for $i = 1,ldots,n$. Now the joint distribution is given by
begin{equation*}
mathbb{P}left(X_{1} = k_1,ldots,X_n = k_nright) = prod_{j=1}^{n}e^{-lambda_j}frac{lambda_j^{k_j}}{k_j!}.
end{equation*}

The characteristic function $varphi_{X_{i}}(t_{i})$ of $X_{i}$ is given by
$$
varphi_{X_{i}}(t_{i}) = e^{lambda_{i}left(e^{it_{i}} - 1 right)}.
$$

Is it right that the characteristic funtion of $(X_{1},ldots,X_n)$ is given by
$$
varphi_{X_{1}}(t_{1})cdotldotsvarphi_{X_{n}}(t_{n}) = e^{sum_{i=1}^{n}lambda_{i}left(e^{it_{i}} -1 right)}?
$$










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$endgroup$

















    1












    $begingroup$


    Let $X_{i}$ be independent Poisson distributed random variables with parameter $lambda_{i} > 0$ for $i = 1,ldots,n$. Now the joint distribution is given by
    begin{equation*}
    mathbb{P}left(X_{1} = k_1,ldots,X_n = k_nright) = prod_{j=1}^{n}e^{-lambda_j}frac{lambda_j^{k_j}}{k_j!}.
    end{equation*}

    The characteristic function $varphi_{X_{i}}(t_{i})$ of $X_{i}$ is given by
    $$
    varphi_{X_{i}}(t_{i}) = e^{lambda_{i}left(e^{it_{i}} - 1 right)}.
    $$

    Is it right that the characteristic funtion of $(X_{1},ldots,X_n)$ is given by
    $$
    varphi_{X_{1}}(t_{1})cdotldotsvarphi_{X_{n}}(t_{n}) = e^{sum_{i=1}^{n}lambda_{i}left(e^{it_{i}} -1 right)}?
    $$










    share|cite|improve this question











    $endgroup$















      1












      1








      1





      $begingroup$


      Let $X_{i}$ be independent Poisson distributed random variables with parameter $lambda_{i} > 0$ for $i = 1,ldots,n$. Now the joint distribution is given by
      begin{equation*}
      mathbb{P}left(X_{1} = k_1,ldots,X_n = k_nright) = prod_{j=1}^{n}e^{-lambda_j}frac{lambda_j^{k_j}}{k_j!}.
      end{equation*}

      The characteristic function $varphi_{X_{i}}(t_{i})$ of $X_{i}$ is given by
      $$
      varphi_{X_{i}}(t_{i}) = e^{lambda_{i}left(e^{it_{i}} - 1 right)}.
      $$

      Is it right that the characteristic funtion of $(X_{1},ldots,X_n)$ is given by
      $$
      varphi_{X_{1}}(t_{1})cdotldotsvarphi_{X_{n}}(t_{n}) = e^{sum_{i=1}^{n}lambda_{i}left(e^{it_{i}} -1 right)}?
      $$










      share|cite|improve this question











      $endgroup$




      Let $X_{i}$ be independent Poisson distributed random variables with parameter $lambda_{i} > 0$ for $i = 1,ldots,n$. Now the joint distribution is given by
      begin{equation*}
      mathbb{P}left(X_{1} = k_1,ldots,X_n = k_nright) = prod_{j=1}^{n}e^{-lambda_j}frac{lambda_j^{k_j}}{k_j!}.
      end{equation*}

      The characteristic function $varphi_{X_{i}}(t_{i})$ of $X_{i}$ is given by
      $$
      varphi_{X_{i}}(t_{i}) = e^{lambda_{i}left(e^{it_{i}} - 1 right)}.
      $$

      Is it right that the characteristic funtion of $(X_{1},ldots,X_n)$ is given by
      $$
      varphi_{X_{1}}(t_{1})cdotldotsvarphi_{X_{n}}(t_{n}) = e^{sum_{i=1}^{n}lambda_{i}left(e^{it_{i}} -1 right)}?
      $$







      probability poisson-distribution characteristic-functions






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      edited Jan 20 at 21:27









      Davide Giraudo

      127k16151264




      127k16151264










      asked Jan 16 at 19:29









      love_mathlove_math

      1615




      1615






















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          $begingroup$

          Yes. The joint characteristic function of the $X_j$ is $Bbb Eexp itcdot X=Bbb Eprod_jexp it_jX_j$. By independence, $Bbb E$ commutes with $prod_j$.






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            $begingroup$

            Yes. The joint characteristic function of the $X_j$ is $Bbb Eexp itcdot X=Bbb Eprod_jexp it_jX_j$. By independence, $Bbb E$ commutes with $prod_j$.






            share|cite|improve this answer









            $endgroup$


















              2












              $begingroup$

              Yes. The joint characteristic function of the $X_j$ is $Bbb Eexp itcdot X=Bbb Eprod_jexp it_jX_j$. By independence, $Bbb E$ commutes with $prod_j$.






              share|cite|improve this answer









              $endgroup$
















                2












                2








                2





                $begingroup$

                Yes. The joint characteristic function of the $X_j$ is $Bbb Eexp itcdot X=Bbb Eprod_jexp it_jX_j$. By independence, $Bbb E$ commutes with $prod_j$.






                share|cite|improve this answer









                $endgroup$



                Yes. The joint characteristic function of the $X_j$ is $Bbb Eexp itcdot X=Bbb Eprod_jexp it_jX_j$. By independence, $Bbb E$ commutes with $prod_j$.







                share|cite|improve this answer












                share|cite|improve this answer



                share|cite|improve this answer










                answered Jan 16 at 19:50









                J.G.J.G.

                27.7k22843




                27.7k22843






























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