Stochastic and fuzzy PERT

Network-planning techniques are considered based on stochastic and fuzzy models of the activity durations. The stochastic versions of PERT are generally intractable, and they cannot be used to draw up tight plans for action. Fuzzy models are closer to reality, simpler to use, but theoretically not well established. The impact of a stochastic and a fuzzy version of PERT is illustrated via a numerical example. Finally, the representation of uncertainty in network planning is discussed, when the activity durations are estimated by human experts.