Program evaluation and review technique: Difference between revisions

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PERT is a method of analyzing the tasks involved in completing a given project, especially the time needed to complete each task, and to identify the minimum time needed to complete the total project. It incorporates uncertainty by making it possible to schedule a project while not knowing precisely the details and [[Duration (project management)|durations]] of all the activities. It is more of an event-oriented technique rather than start- and completion-oriented, and is used more in those projects where time is the major factor rather than cost. It is applied on very large-scale, one-time, complex, non-routine infrastructure and on Research and Development projects.

PERT offers a management tool{{sfn|Kerzner|20092019}}{{rp|497}}, which relies "on arrow and node diagrams of ''activities'' and ''events'': arrows represent the ''activities'' or work necessary to reach the ''events'' or nodes that indicate each completed phase of the total project."<ref name="MB 1968"/>

PERT and CPM are complementary tools, because "CPM employs one time estimation and one cost estimation for each activity; PERT may utilize three time estimates (optimistic, expected, and pessimistic) and no costs for each activity. Although these are distinct differences, the term PERT is applied increasingly to all critical path scheduling."<ref name="MB 1968"/>

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=== Time ===

PERT has defined four types of time required to accomplish an activity:

* ''optimistic time'': the minimum possible time required to accomplish an activity (o) or a path (O), assuming everything proceeds better than is normally expected{{sfn|Kerzner|20092019}}{{rp|512}}

* ''pessimistic time'': the maximum possible time required to accomplish an activity (p) or a path (P), assuming everything goes wrong (but excluding major catastrophes).{{sfn|Kerzner|20092019}}{{rp|512}}

* ''most likely time'': the best estimate of the time required to accomplish an activity (m) or a path (M), assuming everything proceeds as normal.{{sfn|Kerzner|20092019}}{{rp|512}}

* ''expected time'': the best estimate of the time required to accomplish an activity (te) or a path (TE), accounting for the fact that things don't always proceed as normal (the implication being that the expected time is the average time the task would require if the task were repeated on a number of occasions over an extended period of time).{{sfn|Kerzner|20092019}}{{rp|512-513}}

::: <math> te = \frac{o + 4m + p} 6 </math>

:::<math>TE = \sum_{i=1}^n te_i</math>

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| last = Kerzner

| author-link = Harold Kerzner

| year = 20092019

| title = Project Management: A Systems Approach to Planning, Scheduling, and Controlling

| edition = 10th