A PERT (Program Evaluation and Review Technique) chart is a project management tool used to plan, schedule, and manage complex projects, allowing a convenient and accurate way to visualize each task in a project in either a series of interdependent steps or as parallel activities. It is sometimes known as an activity network diagram.
A PERT chart consists of nodes (a box or a circle) that each represent a project task or activity. Arrows connect the nodes, showing the flow of the project from one task to another. The information provided by the chart helps project managers look ahead and see potential roadblocks within a project. Those roadblocks include issues related to:
- The time needed for each task as well as the overall time needed for the entire project
- Potential bottlenecks where lack of resources could become an issue
- Phases of the project where communication between individuals or teams will become critical for project success
- Task for especially high risk where managers will need to ensure teams have the proper resources and tools, clear communication, and support from management needed to avoid delays or misunderstandings that can derail a project.
PERT Charts and Project Management
The issue of time is one of the main aspects of a project that a PERT chart addresses. They typically show three different potential outcomes when it comes to the time needed to complete individual tasks and the overall project: the most likely, optimistic and pessimistic timelines.
This comes into play when executives want to know the timeline for completion of an important project. Many issues could be on the line with a project, including the money invested in completing it or the impact of the project’s results on business strategy. PERT charts allow project managers to present executives with best case and worst case scenarios. This includes a representation of the most optimistic time (most things go right), the most pessimistic time (many things go wrong) and a most likely time (a balance between the two).
Teams should create PERT charts at the beginning of a project, giving them a way to accurately visualize the project timeline, identify the critical path a project needs to take and predict potential bottlenecks. A PERT chart is a living document that teams should update throughout the project. These updates help the project team stay on track and make adjustments as needed.
Situations where a PERT chart can be particularly useful include:
- Large-scale projects: PERT charts are ideal for large-scale projects that require a considerable amount of planning and coordination.
- Projects with multiple tasks. Projects with multiple activities also have critical dependencies between each tasks and more uncertainty with the timeline. A PERT chart maps the activities and allows project managers to quickly identify the critical path a project must follow and which tasks are of the most importance when it comes to project success.
- Projects with strict timelines: PERT charts can help teams stay on schedule with projects that have strict deadlines or contractual obligations. The chart helps project managers identify potential delays and take proactive measures to avoid them.
- Complex projects: PERT charts are especially useful for projects that involve multiple stakeholders, significant resources and have several interdependent components.
For Lean Six Sigma practitioners, a PERT chart is a common tool used in the planning stages of a project that provides the “big picture” and keeps a project moving forward on schedule. It helps reduce the risks associated with projects, especially in providing a way to anticipate and address potential project bottlenecks and constraints.
Use case: Let’s say that you are working on a project and your boss wants to know how long the project is going to take. You could give your boss an idea of how long it will take off the top of your head, but since there is a lot of money on the line, you know that your boss wants a more scientific way of determining how long the project is likely to take. With the pert chart, you are going to calculate three things. You are going to calculate the most likely time. But, you want to give your boss an idea of a range of times. In other words, you want to give him or her the ‘best case’ and the ‘worst case’ scenarios. So, you will be calculating the most optimistic time and the most pessimistic time. From that you can calculate some guard bands around the most likely time.
