Program evaluation and review technique or PERT is a way to see and analyze the relationships between the tasks of a project. It uses a network diagram showing the activities (tasks) and which must occur before others (predecessors). The estimated durations for each activity are added, and then the critical path, slack and float can be calculated along with the critical path. The technique was developed by the U.S. Navy in the 1950s.
Comparisons of the PERT diagram and the work as it progresses can be used as a technique to monitor the project's performance. And data from stages in the project may help to make estimates for similar tasks at later stages or other projects more accurate.
PERT uses a formula to estimate the expected time (te) for each activity. It is a weighted average using the optimistic (o) or shortest possible, pessimistic (p) or longest excluding major catastrophes, and most likely (m) weighted at 4 times the p and o estimates:
- te = (o + 4m + p) ÷ 6
Related: Gantt chart, project management software, three-point estimating, critical path method, float, slack, activity diagram, activity duration estimates, early start time (ES), early finish time (EF), late start time (LS), late finish time (LF)