Chi-squared distribution
Probability density function

The probability density function (pdf) of the chi-squared distribution is

where Γ (k / 2) {\textstyle \Gamma (k/2)} denotes the gamma function, which has closed-form values for integer k {\displaystyle k}.

For derivations of the pdf in the cases of one, two and k {\displaystyle k} degrees of freedom, see Proofs related to chi-squared distribution.
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