What Is a Program Evaluation Review Technique (PERT) Chart?

A Program Evaluation Review Technique (PERT) chart is a valuable tool in project management that visually represents the timeline and tasks involved in completing a project. First developed by the U.S. Navy in the 1950s during the Polaris nuclear submarine project, PERT charts have since found applications in various fields due to their ability to delineate complex project tasks and timelines effectively.

Key Features of PERT Charts

A PERT chart is made up of nodes (represented by circles or rectangles) and vectors (lines connecting the nodes):

• Nodes: Each node symbolizes a specific project event or milestone.
• Vectors: Lines that connect these nodes illustrate tasks and their dependencies. For example, if Task A flows into Task B, Task A must be completed before Task B can commence.

Understanding Task Dependencies

A crucial element of PERT charts is the recognition of task dependencies. These are categorized into:

• Sequential Tasks: Where one task must be finished before another can start.
• Parallel Tasks: Tasks that can run concurrently, independent of one another.

A well-constructed PERT chart can help project managers visualize the flow of the project, identify critical paths—the longest series of tasks that must be completed on time for the whole project to meet deadlines—and engage in informed resource allocation.

How PERT Charts Work

Creating a PERT chart involves collecting all tasks necessary for project completion and estimating the time required for each task based on various scenarios:

1. Optimistic Time: The minimum amount of time needed to complete a task.
2. Pessimistic Time: The maximum time that might be required if difficulties arise.
3. Most Likely Time: A realistic estimate based on current project protocols.
4. Expected Time: A weighted average considering obstacles that could occur.

Project managers can develop accurate timelines and establish a comprehensive resource and budget plan from the gathered data.

Interpreting a PERT Chart

• Visual Flow: The flow of arrows indicates the project sequence.
• Dummy Activities: Represented by dotted lines—these may not contribute directly to the project path but help clarify relationships between tasks.
• Time Allocations: Estimates related to each task are indicated within the vectors.

PERT vs. Gantt Charts

While both PERT and Gantt Charts provide timelines for project tasks, they differ primarily in layout and functionality. Gantt charts, created earlier in the 20th century by Henry Gantt, display tasks in horizontal bars, which help track time and show dependencies across a simple timeline. PERT charts, on the other hand, excel in showing task dependencies and are often preferred when project complexities arise.

Advantages and Disadvantages of PERT Charts

Advantages

• Resource Evaluation: Allows managers to analyze both time and resources needed to complete a project.
• Cross-departmental Collaboration: Incorporates information from various departments, fostering collaboration and accountability.
• Enhanced Communication: Clear visual representation improves readability and communication among project stakeholders.
• Scenario Planning: Facilitates what-if analyses—allowing project managers to anticipate potential obstacles and plan accordingly.

Disadvantages

• Subjectivity of Data: Since estimates are often based on opinions, they may be unreliable.
• Heavy Workload: Requires significant time and resources to create and maintain, needing continual updates.
• Limited Focus on Financials: Primarily emphasizes deadlines and timelines, potentially overlooking financial implications.

Creating a PERT Chart

Creating a PERT chart can be straightforward using various software tools. Programs like Microsoft Excel offer a simple solution, while specialized software like Lucidchart provides templates tailored for PERT chart development.

Steps to Create a PERT Chart:

1. List Out All Tasks: Identify the key tasks involved in the project.
2. Define Dependencies: Determine the relationships between tasks.
3. Estimate Time Frames: Provide time estimates for each task using the four time categories.
4. Draw the Chart: Utilize graphing software to plot nodes and connect them via vectors.

Conclusion

For project managers facing the challenges of complex projects, PERT charts offer a structured way to model tasks and timelines effectively. This tool enables enhanced communication, thoughtful planning, and resource allocation. With various software tools available, creating PERT charts has never been easier, making them an essential part of the project management arsenal for those aiming for successful project outcomes.