PERT estimate is an under-estimate. Visual evidence from computational statistics

PERT (Program Evaluation and Review Technique) estimates are used in project management to estimate the total project duration and cost. One limitation of PERT estimates is that it underestimates the true mean. This note provides a visual appreciation of this limitation by performing a Monte Carlo simulation of a simple project network. It also explores how Monte Carlo simulations can be useful when other assumptions of PERT estimates (independence of tasks) are not met.