Gantt and PERT Charts

Gantt and PERT charts are visualization tools commonly used by project managers to control and administer the tasks required to complete a project.

The Gantt chart, developed by Charles Gantt in 1917, focuses on the sequence of tasks necessary for completion of the project at hand. Each task on a Gantt chart is represented as a single horizontal bar on an X-Y chart. The horizontal axis (X-axis) is the time scale over which the project will endure. Therefore, the length of each task bar corresponds to the duration of the task, or the time necessary for completion. Arrows connecting independent tasks reflect the relationships between the tasks it connects. The relationship usually shows dependency where one task cannot begin until another is completed. The resources necessary for completion are also identified next to the chart. The Gantt chart is an excellent tool for quickly assessing the status of a project. The following Gantt chart was developed using MS Project for developing a proposal.

gantt.jpg (170856 bytes)

Making this chart is a pretty self explanatory task. Almost all controls are available by double clicking task names in the column on the left. This chart shows the resources, completion (shown by the horizontal black line within the task bar), and prerequisite relationships….all controllable through double clicking appropriate task name on the left. You can change the time scale on the top by right click….time scale option. Its basically controlled by typical Microsoft actions used in any MS application.

PERT (Program Evaluation and Review Technique) charts were first developed in the 1950s by the Navy to help manage very large, complex projects with a high degree of intertask dependency. Classical PERT charting is used to support projects that are often completed using an assemply line approach. MS Project can create a PERT chart from a Gantt chart. The PERT below is another representation of the Proposal project shown above.

pert.jpg (151487 bytes)

Again, the representation above is relatively self explanatory. The completed tasks have been crossed out while partially completed tasks have one slash through them. The tasks also show duration, beginning date and ending date.

The critical path (shown in red) is a series of tasks that must be completed on schedule for a project to finish on schedule. Each task on the critical path is a critical task. Most tasks in a typical project have some slack and can therefore be delayed a little without affecting the project finish date. Those tasks that cannot be delayed without affecting the project finish date are the critical tasks. As you modify tasks to resolve overallocations or other problems in your schedule, be aware of the critical tasks and that changes to them will affect your project finish date.


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