Definition:Gamma Distribution

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Definition

Let $X$ be a continuous random variable on a probability space $\struct {\Omega, \Sigma, \Pr}$.

Let $\Img X = \R_{\ge 0}$.


$X$ is said to have a Gamma distribution if it has probability density function:

$\map {f_X} x = \dfrac {\beta^\alpha x^{\alpha - 1} e^{-\beta x} } {\map \Gamma \alpha}$

for $\alpha, \beta > 0$, where $\Gamma$ is the Gamma function.


This is written:

$X \sim \map \Gamma {\alpha, \beta}$




Also defined as

The gamma distribution can also be seen in the form:

$\map f x = \dfrac {x^{\alpha - 1} e^{-\alpha / \beta} } {\beta^\alpha \map \Gamma \alpha}$


Also see

  • Results about the Gamma distribution can be found here.


Sources