PERT (Program Evaluation and Review Technique) uses a weighted average of the optimistic time (TO), the most likely time (TM), and the pessimistic time (TP) of a task or activity to get the expected time (TE). For the purpose of determining TE, the following equation is used:
TE = (TO + 4TM + TP) / 6
The computation is based on the premise that the best-case scenario corresponds to the optimistic time, the worst-case scenario to the pessimistic time, and the most probable scenario to the most likely time. The uncertainty of the task or activity is accounted for by averaging these three times to arrive at an estimate of the expected time.
The assumption underlying the 1 for TO, 4 for TM, and 1 for TP weights is that the most likely time is the most accurate estimate of the expected time, while the optimistic and pessimistic times are less accurate. By determining the range across which a project’s tasks and activities can be completed, project managers can make better judgements about scheduling and resource allocation, which is helpful for both planning and managing risks associated with the project.
It’s true that PERT has some limitations and criticisms, though. The optimistic, most likely, and pessimistic times are weighted and averaged to arrive at the predicted time, however, this may not always reflect the actual time required to complete the task. Another issue with PERT is that it can take a long time and necessitate a lot of data collection, both of which might be challenging or unrealistic for some projects.
Some have also pointed out that PERT ignores the fact that the completion of one task can have repercussions on the completion of others. For projects with intricate job dependencies, this can be a serious problem because it leads to erroneous time estimations.
In conclusion, PERT is an effective method for managing projects, but its strengths and weaknesses must be considered. To acquire a more realistic view of project completion times and to account for task interdependencies, it may be essential to supplement PERT with other project management methodologies, such as critical path analysis.
