PERT-Chart

A Programme Evaluation and Review Technique (PERT) chart is one of the basic planning tools of project management. It is used to roughly structure the course of a project. It represents the activities in a project in their logical dependencies and in their chronological sequence graphically or in tabular form.

When is the planning technique suitable? What disadvantages does it have and how do you create your network? Answers can be found in this article.

The PERT chart goes beyond the information content of the work breakdown structure. While the work breakdown structure only shows the logical relationships between the project activities, the PERT chart also shows the chronological order of the individual activities. In the classic net plan, events and activities are represented as nodes and their relationship to each other is visualized with arrows. This creates a net of task packages and activities that gives the method its name.

In most cases, the operations are sorted by time, but not scheduled. Exceptions are Gantt charts and bar diagrams. They can be understood as a special form of net plan technology. In bar charts or Gantt charts, activities are displayed as bars on a time axis.

Goal and purpose

The net plan is an effective visualization tool. It gives a good overview of time, costs and resources of the project. In analog project planning, the net plan was the tool of choice for calculating the start and end times of task packets, the critical path, and time buffers (total buffers or free buffers in the net plan). Nowadays, project management tools calculate these times automatically. However, a basic understanding of the net plan methodology is still helpful for the effective use of the software.

The representation of a project using the net plan technique has several objectives:

• Duration: Determination of the total project duration
• Risks: Determination of the critical path
• Opportunities: Identification of possible potentials for a faster completion of the project
• Scheduling: Creation of a basis for scheduling

Overview of the net plan techniques

How a net plan is created depends on the net plan technology used. There are four types of net plans, based on different methodologies.

1. event-on-node (in simplified form: milestone plan)
2. activity-on-node
3. activity-on-arrow
4. conditional diagram

In practice, the event-on-node PERT chart and the activity-on-node PERT chart are used. The latter is the model supported by most IT solutions. For the event-node-netplan the Programme Evaluation and Review Technique – PERT is used. Therefore, it is often referred to as a PERT diagram rather than an event-on-node-plan. Some project management tools also incorrectly refer to the activity-on-node network as PERT. The activity-on-arrow net plan focuses on the visualization of the critical path, but is hardly used anymore. The conditional diagram at least partially incorporates risk management by considering future decisions for planning. In practice, however, it is not used and is not supported by common project management software.

Advantages and Disadvantages of the PERT charts

Whoever uses the PERT chart in project management has a powerful tool at hand. However, net plan technology is not always the best planning method. In some cases, the disadvantages outweigh the advantages. Whether the method is suitable must be checked individually.

Advantages

• The preparation makes it necessary to think through the entire project and not just individual sub-areas. In this way, open points become visible.
• The network plan creates a meaningful overview of all project activities and their mutual dependencies.
• The plan can be easily updated.
• A relatively exact scheduling and thus cost saving is possible.
• Bottlenecks (critical path and buffer) are easy to recognize.
• The network can be developed independently of schedule assumptions.
• The plan is a clear communication tool for the project managers.

Disadvantages

• The creation is relatively complex.
• The presentation requires training in order to fully capture the information content.
• The more detailed the network, the higher the control effort to avoid planning errors.

The method is oversized for small projects. Here the special forms of the bar diagram or Gantt charts are more user-friendly.

How to create a PERT chart for your project

Today, nobody has to manually create a net plan anymore. It is also not the best and most efficient way to create a net plan with Excel. Instead it is recommended to use a Project Management Software.

In every professional project management application the net plan should be integrated as one view of many. It is crucial to find the right tool that makes data entry easy and visualizes information in a meaningful way. Applications often provide different net plan templates. Merlin Project for example offers mind-map, organzational chart and net plan view. As individual as each project may appear, blueprints can be identified at the end. Using templates for your net plan can save a lot of time.

Conclusion

Net plan technology is one of the core tools in project management. It is taught in every project management training course. To penetrate the systematics of network plans requires initial training. However, it is worth the effort, especially for larger projects. With the right software, creating a PERT chart is no longer as time-consuming as it used to be in analogous times. For smaller projects, however, there are simpler planning instruments for visualizing time, costs and resources.