PsiPearson5 (α,β) is a distribution with a lower bound of 0, and density similar to that of the LogNormal distribution. The Pearson5 distribution is sometimes called the Inverse Gamma distribution. It can be used to model time delays when these can possibly take on unbounded (or very large) values.
Alternate Formulation: PsiPearson5Alt
PsiPearson5Alt is the PsiPearson5 distribution defined through alternative arguments. Two parameters are required and both must be chosen from the following list: two different percentiles, shape or scale.