in PROGRAM EVALUATION AND REVIEW TECHNIQUE (PERT), a weighted average time that is widely used in a real life application of PERT to a complex project, where the completion times for activities are not certain. First, estimate three possible duration times for each activity: an optimistic, a most likely, and a pessimistic time. A weighted average of these three time estimates is then calculated to establish the expected time for the activity. The formula applies to a weight of one to both the optimistic and the pessimistic estimates and a weight of four to the most likely estimate