# Work out the variance of the gamma

1. Aug 29, 2009

### gerv13

Hi, I'm trying to work out the variance of the gamma(I'm up the the part where you multiply $$x^2$$ by the function), but i don't know how to work out what

$$\gamma(\alpha + 2)$$ equals to

i know im supposed to use the fact that $$\gamma(\alpha + 1) = \alpha \gamma(\alpha)$$

but i dont understand what to do, please help

2. Aug 29, 2009

### HallsofIvy

Staff Emeritus
Re: gamma

It's not clear whether you are talking about the gamma probability distribution or the gamma function. The gamma function has the property that $\Gamma(\alpha+1)= \alpha\Gamma(\alpha)$ but is normally represented by the capital $\Gamma$, not $\gamma$.

In any case, $\Gamma(\alpha+ 2)= \Gamma(\alpha+1+ 1)$$= (\alpha+1)\Gamma(\alpha+1)= (\alpha+ 1)\alpha\Gamma(\alpha)$.

3. Aug 29, 2009

### tickle_monste

Re: gamma

I'm not sure either, but I have to guess its the probability distribution.

4. Aug 29, 2009

### gerv13

Re: gamma

yupp i actually meant $$\Gamma$$ sorry about that. but thanks for the help

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