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.


Critical Path on an AoA diagram

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
Pert chart colored-pd-by-Jeremykemp

PERT network chart for a seven-month project with five milestones (10 through 50) and six activities (A through F).

After calculating the expected times, a network diagram based on the dependencies with the times is created. This can be used to calculate the critical path.

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)

5n PERT graph with critical path2-pd

A simple PERT chart (activity-on-node diagram‏‎) with durations shown on the paths, and the critical path shown in red. (Public domain image courtesy of the Wikimedia Commons)

External linksEdit