Program Evaluation and Review Technique

What is the Program Evaluation and Review Technique?

The Program Evaluation and Review Technique (PERT) is a network-based project management technique that focuses on the scheduling and coordination of tasks. It supports project managers in estimating the expected duration of a project even when the durations of individual activities are not yet known precisely. To achieve this, PERT uses multiple time estimates per activity and calculates an expected time value from them.

In the classical PERT calculation, three time estimates are defined for each task:

• Optimistic duration (o): The time achievable under the best possible conditions
• Most likely duration (m): The most realistic expected time
• Pessimistic duration (p): The time required under unfavorable conditions

From these values, an expected time value is calculated, which is then used in the network diagram to determine the overall project duration.

Objectives and Benefits

Applying PERT offers several advantages:

• It provides a realistic estimate of the project duration even when individual activities are subject to uncertainty.
• It makes dependencies between project tasks visible and helps identify scheduling bottlenecks.
• PERT diagrams support communication within the project team by graphically representing complex workflows.
• The method can be used to model different scenarios and analyze risks in time planning.

Positioning in Project Management

PERT is often applied in large, complex projects, especially when there is uncertainty regarding the duration of individual work packages, such as in research, development, or innovation projects. It complements classical planning approaches and is closely related to the Critical Path Method (CPM). While CPM works with fixed duration estimates, PERT enables a statistically based understanding of time under uncertainty.

Diagram and Visualization

A typical PERT diagram visualizes project tasks as a network of events and activities. Milestones or intermediate goals are represented by nodes, while arrows indicate the dependencies and sequence of activities. This graphical representation makes it easier to identify priorities and dependencies within complex projects.

Difference from Related Methods

CPM (Critical Path Method): Uses single, fixed time estimates to determine the critical path and is therefore more deterministic, whereas PERT uses multiple time estimates and follows a probabilistic approach.

Gantt chart: Displays timelines and milestones in a linear format but does not incorporate the three-point estimation used in PERT.