Program Evaluation and Review Technique
Program Evaluation and Review Technique, or PERT for short, refers to a project planning method for the temporal analysis and evaluation of activities within a project. It was developed in the 1950s in parallel with the Critical Path Method and is used specifically to estimate project durations when there are uncertainties in time specifications.
What is the Program Evaluation and Review Technique?
The Program Evaluation and Review Technique method is a network planning technique that focuses on the scheduling and coordination of tasks. It supports project managers in determining the expected time requirements of a project, even if the duration of individual activities is not yet precisely known. To this end, PERT uses several time estimates per activity and calculates an expected time value from them.
In classic PERT calculation, three time values are recorded for each task:
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- Optimistic duration (o): Time achievable under the best conditions
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- Most likely duration (m): The most realistically expected time
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- Pessimistic duration (p): Duration under unfavorable conditions
The expected time value is derived from these values, which is then entered into the network plan and used to determine the project duration.
Objectives and Benefits
The application of PERT brings several advantages:
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- It provides a realistic estimate of the project duration, even when individual activities are still uncertain.
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- It makes dependencies between project tasks visible and helps to identify bottlenecks in the schedule.
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- PERT charts support communicative coordination within the project team, as they represent complex processes graphically.
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- The method can be used to map various scenarios and analyze risks in scheduling.
Classification in Project Management
PERT is frequently used in large, complex projects, especially when there is still uncertainty regarding the duration of individual work packages, such as in research, development, or innovation projects. It complements classic planning approaches and is closely related to the Critical Path Method (CPM). While CPM works with fixed duration estimates, PERT enables a statistically supported understanding of time under uncertainty.
Diagram and Visualization
A typical PERT chart visualizes project tasks as a network of events and activities. Milestones or intermediate goals are represented by nodes; arrows show the dependencies and sequences of the activities. This graphical representation facilitates the identification of priorities and dependencies within complex projects.
Difference to Related Methods
CPM (Critical Path Method): Uses single, fixed time values to determine the critical path and is therefore more deterministic; PERT uses multiple time values and is probabilistically oriented.
Gantt Chart: Represents timelines and milestones linearly, but does not offer a three-point estimate like PERT.