English: A plot of the cumulative distribution function for the scaled chi-squared probability distribution, the probability distribution of the sample variance s²,

${\displaystyle s^{2}={\frac {\;\sigma ^{2}}{\nu }}\;\chi _{\nu }^{2}}$

where s² is the mean of the squares of ν independent normal distributions of mean 0 and standard deviation σ; plotted here for the case σ = 1.0.

Equivalently this is also a plot of the c.d.f. for the variance ratio s²/σ² for any value of σ.