What is the best distribution that describe the variances $\sigma^2(x)$?

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I'm studying a numerical variances $\sigma^2(x)$. For each samples I have more than one hundred of variances.

I'm looking for the distribution that can describe them. I think is not Gaussian, because $\sigma^2(x) \ge 0$.

The question is: for computing the confidence interval is better use a Rayleigh distribution, a chi-squared distribution or an other again?