PsiPert Distribution

PsiPert (a,c,b,...)

PsiPert (a,c,b) is a form of the Beta distribution, often used to estimate project comple­tion times in the Program Evaluation and Review Technique, where a is the minimum time, b is the maximum time, and c is the most likely time.  These parameters are used to compute the shape parameters α1,α2 used in the PsiBeta function, as shown below.

Alternate Formulation:  PsiPertAlt

PsiPertAlt is the PsiPert distribution defined through alternative arguments.  Three parameters are required which must be chosen from the following list:  3 different percentiles, mean, var, min, likely or max.