An approximation of the activity duration distribution in PERT

PERT is widely used as a tool for managing large-scale projects. The tradit ional PERT approach uses the beta distribution as the distribution of activ ity duration and estimates the mean and the variance of activity duration b ased on the "pessimistic", "optimistic" and "most likely" time estimates, S everal authors have modified the original three point PERT estimators to im prove the accuracy of the estimates. This article proposes new approximatio ns for the mean and the variance of activity based on "pessimistic". "optim istic" and "most likely" time estimates. By numerical comparison with actua l values, the proposal is shown as more accurate than the original PERT est imates and its modifications. Another advantage of the proposed approximati on is that it requires no assumptions about the parameters of the beta dist ribution as in the case of existing ones.