Calculating UMVUE for Poisson distribution












2












$begingroup$


I've started to learn methods of finding UMVUE distribution. I found some nice examples on this site.



I got stuck while evaluating UMVUE for Poisson distribution for a parametric function $g(theta)$.
enter image description here



How did the author get
$$sum_{t=o}^infty frac{h(t) n^t}{t!} theta^t = e^{n theta}g(theta)?$$
I thought
$$mathbb{E}(h(x)) = g(theta)$$
should be considered.










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$endgroup$








  • 1




    $begingroup$
    I will just mention that there is a discussion on meta about the newly created (umvue) tag. (It seemed reasonable to let the tag-creator know about this.)
    $endgroup$
    – Martin Sleziak
    Jan 10 at 8:35
















2












$begingroup$


I've started to learn methods of finding UMVUE distribution. I found some nice examples on this site.



I got stuck while evaluating UMVUE for Poisson distribution for a parametric function $g(theta)$.
enter image description here



How did the author get
$$sum_{t=o}^infty frac{h(t) n^t}{t!} theta^t = e^{n theta}g(theta)?$$
I thought
$$mathbb{E}(h(x)) = g(theta)$$
should be considered.










share|cite|improve this question











$endgroup$








  • 1




    $begingroup$
    I will just mention that there is a discussion on meta about the newly created (umvue) tag. (It seemed reasonable to let the tag-creator know about this.)
    $endgroup$
    – Martin Sleziak
    Jan 10 at 8:35














2












2








2





$begingroup$


I've started to learn methods of finding UMVUE distribution. I found some nice examples on this site.



I got stuck while evaluating UMVUE for Poisson distribution for a parametric function $g(theta)$.
enter image description here



How did the author get
$$sum_{t=o}^infty frac{h(t) n^t}{t!} theta^t = e^{n theta}g(theta)?$$
I thought
$$mathbb{E}(h(x)) = g(theta)$$
should be considered.










share|cite|improve this question











$endgroup$




I've started to learn methods of finding UMVUE distribution. I found some nice examples on this site.



I got stuck while evaluating UMVUE for Poisson distribution for a parametric function $g(theta)$.
enter image description here



How did the author get
$$sum_{t=o}^infty frac{h(t) n^t}{t!} theta^t = e^{n theta}g(theta)?$$
I thought
$$mathbb{E}(h(x)) = g(theta)$$
should be considered.







statistics parameter-estimation






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share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Jan 12 at 11:47









Saad

19.7k92352




19.7k92352










asked Jan 9 at 17:27









HendrraHendrra

1,163516




1,163516








  • 1




    $begingroup$
    I will just mention that there is a discussion on meta about the newly created (umvue) tag. (It seemed reasonable to let the tag-creator know about this.)
    $endgroup$
    – Martin Sleziak
    Jan 10 at 8:35














  • 1




    $begingroup$
    I will just mention that there is a discussion on meta about the newly created (umvue) tag. (It seemed reasonable to let the tag-creator know about this.)
    $endgroup$
    – Martin Sleziak
    Jan 10 at 8:35








1




1




$begingroup$
I will just mention that there is a discussion on meta about the newly created (umvue) tag. (It seemed reasonable to let the tag-creator know about this.)
$endgroup$
– Martin Sleziak
Jan 10 at 8:35




$begingroup$
I will just mention that there is a discussion on meta about the newly created (umvue) tag. (It seemed reasonable to let the tag-creator know about this.)
$endgroup$
– Martin Sleziak
Jan 10 at 8:35










1 Answer
1






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oldest

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3












$begingroup$

Observe
$$sum_{t=0}^{infty}dfrac{h(t)n^t}{t!}theta^t = sum_{t=0}^{infty}dfrac{h(t)(ntheta)^t}{t!}text{.}$$
Set $lambda = ntheta$. Then
$$sum_{t=0}^{infty}dfrac{h(t)(ntheta)^t}{t!} = sum_{t=0}^{infty}dfrac{h(t)lambda^t}{t!} = sum_{t=0}^{infty}dfrac{h(t)e^{-lambda}e^{lambda}lambda^t}{t!} = e^{lambda}sum_{t=0}^{infty}left[h(t)cdot dfrac{e^{-lambda}lambda^t}{t!}right]text{.}$$
Since $T sim P(lambda)$ (using the notation in your image), then
$$sum_{t=0}^{infty}left[h(t)cdot dfrac{e^{-lambda}lambda^t}{t!}right] = mathbb{E}[h(T)] = g(theta)$$
due to unbiasedness, hence
$$sum_{t=0}^{infty}dfrac{h(t)n^t}{t!}theta^t = e^{lambda}g(theta)=e^{ntheta}g(theta)text{.}$$






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$endgroup$













  • $begingroup$
    Thank you! That's an awesome solution
    $endgroup$
    – Hendrra
    Jan 9 at 17:42











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1 Answer
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1 Answer
1






active

oldest

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active

oldest

votes






active

oldest

votes









3












$begingroup$

Observe
$$sum_{t=0}^{infty}dfrac{h(t)n^t}{t!}theta^t = sum_{t=0}^{infty}dfrac{h(t)(ntheta)^t}{t!}text{.}$$
Set $lambda = ntheta$. Then
$$sum_{t=0}^{infty}dfrac{h(t)(ntheta)^t}{t!} = sum_{t=0}^{infty}dfrac{h(t)lambda^t}{t!} = sum_{t=0}^{infty}dfrac{h(t)e^{-lambda}e^{lambda}lambda^t}{t!} = e^{lambda}sum_{t=0}^{infty}left[h(t)cdot dfrac{e^{-lambda}lambda^t}{t!}right]text{.}$$
Since $T sim P(lambda)$ (using the notation in your image), then
$$sum_{t=0}^{infty}left[h(t)cdot dfrac{e^{-lambda}lambda^t}{t!}right] = mathbb{E}[h(T)] = g(theta)$$
due to unbiasedness, hence
$$sum_{t=0}^{infty}dfrac{h(t)n^t}{t!}theta^t = e^{lambda}g(theta)=e^{ntheta}g(theta)text{.}$$






share|cite|improve this answer











$endgroup$













  • $begingroup$
    Thank you! That's an awesome solution
    $endgroup$
    – Hendrra
    Jan 9 at 17:42
















3












$begingroup$

Observe
$$sum_{t=0}^{infty}dfrac{h(t)n^t}{t!}theta^t = sum_{t=0}^{infty}dfrac{h(t)(ntheta)^t}{t!}text{.}$$
Set $lambda = ntheta$. Then
$$sum_{t=0}^{infty}dfrac{h(t)(ntheta)^t}{t!} = sum_{t=0}^{infty}dfrac{h(t)lambda^t}{t!} = sum_{t=0}^{infty}dfrac{h(t)e^{-lambda}e^{lambda}lambda^t}{t!} = e^{lambda}sum_{t=0}^{infty}left[h(t)cdot dfrac{e^{-lambda}lambda^t}{t!}right]text{.}$$
Since $T sim P(lambda)$ (using the notation in your image), then
$$sum_{t=0}^{infty}left[h(t)cdot dfrac{e^{-lambda}lambda^t}{t!}right] = mathbb{E}[h(T)] = g(theta)$$
due to unbiasedness, hence
$$sum_{t=0}^{infty}dfrac{h(t)n^t}{t!}theta^t = e^{lambda}g(theta)=e^{ntheta}g(theta)text{.}$$






share|cite|improve this answer











$endgroup$













  • $begingroup$
    Thank you! That's an awesome solution
    $endgroup$
    – Hendrra
    Jan 9 at 17:42














3












3








3





$begingroup$

Observe
$$sum_{t=0}^{infty}dfrac{h(t)n^t}{t!}theta^t = sum_{t=0}^{infty}dfrac{h(t)(ntheta)^t}{t!}text{.}$$
Set $lambda = ntheta$. Then
$$sum_{t=0}^{infty}dfrac{h(t)(ntheta)^t}{t!} = sum_{t=0}^{infty}dfrac{h(t)lambda^t}{t!} = sum_{t=0}^{infty}dfrac{h(t)e^{-lambda}e^{lambda}lambda^t}{t!} = e^{lambda}sum_{t=0}^{infty}left[h(t)cdot dfrac{e^{-lambda}lambda^t}{t!}right]text{.}$$
Since $T sim P(lambda)$ (using the notation in your image), then
$$sum_{t=0}^{infty}left[h(t)cdot dfrac{e^{-lambda}lambda^t}{t!}right] = mathbb{E}[h(T)] = g(theta)$$
due to unbiasedness, hence
$$sum_{t=0}^{infty}dfrac{h(t)n^t}{t!}theta^t = e^{lambda}g(theta)=e^{ntheta}g(theta)text{.}$$






share|cite|improve this answer











$endgroup$



Observe
$$sum_{t=0}^{infty}dfrac{h(t)n^t}{t!}theta^t = sum_{t=0}^{infty}dfrac{h(t)(ntheta)^t}{t!}text{.}$$
Set $lambda = ntheta$. Then
$$sum_{t=0}^{infty}dfrac{h(t)(ntheta)^t}{t!} = sum_{t=0}^{infty}dfrac{h(t)lambda^t}{t!} = sum_{t=0}^{infty}dfrac{h(t)e^{-lambda}e^{lambda}lambda^t}{t!} = e^{lambda}sum_{t=0}^{infty}left[h(t)cdot dfrac{e^{-lambda}lambda^t}{t!}right]text{.}$$
Since $T sim P(lambda)$ (using the notation in your image), then
$$sum_{t=0}^{infty}left[h(t)cdot dfrac{e^{-lambda}lambda^t}{t!}right] = mathbb{E}[h(T)] = g(theta)$$
due to unbiasedness, hence
$$sum_{t=0}^{infty}dfrac{h(t)n^t}{t!}theta^t = e^{lambda}g(theta)=e^{ntheta}g(theta)text{.}$$







share|cite|improve this answer














share|cite|improve this answer



share|cite|improve this answer








edited Jan 9 at 17:46

























answered Jan 9 at 17:34









ClarinetistClarinetist

10.9k42778




10.9k42778












  • $begingroup$
    Thank you! That's an awesome solution
    $endgroup$
    – Hendrra
    Jan 9 at 17:42


















  • $begingroup$
    Thank you! That's an awesome solution
    $endgroup$
    – Hendrra
    Jan 9 at 17:42
















$begingroup$
Thank you! That's an awesome solution
$endgroup$
– Hendrra
Jan 9 at 17:42




$begingroup$
Thank you! That's an awesome solution
$endgroup$
– Hendrra
Jan 9 at 17:42


















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