InverseChiSquareDistribution
InverseChiSquareDistribution[ν] represents an inverse χ² distribution with ν degrees of freedom.
InverseChiSquareDistribution[ν, ξ]represents a scaled inverse χ² distribution with ν degrees of freedom and scale ξ.
Examples
dist = InverseChiSquareDistribution[5];
Mean[dist]Please visit the official Wolfram Language Reference for more details.