Project 2007: Estimating Task Durations Using the PERT Formula (Part 2 of 2)

When you use the PERT Entry Form to estimate and then enter estimated durations for your project's tasks, those durations are added to your project file under PERT Analysis fields. In fact, you can view those fields using one of the first three buttons on the PERT Analysis toolbar.

There are three options, Optimistic Gantt, Expected Gantt, and Pessimistic Gantt.

Optimistic Gantt

• This button displays the Gantt Chart along with the PA_Optimistic Case table. The Opt Duration fields of any task that uses the PERT Form calculation is displayed and the project's Gantt Chart is updated to reflect the most optimistic outcome.

Expected Gantt

• This button displays the Gantt Chart along with the Entry table. The Exp Duration fields of any task that uses the PERT Form calculation is displayed and the project's Gantt Chart is updated to reflect the expected outcome.

Pessimistic Gantt

• This button displays the Gantt Chart along with the PA_Pessimistic Case table. The Pes Duration fields of any task that uses the PERT Form calculation is displayed and the project's Gantt Chart is updated to reflect the most pessimistic outcome.
• Viewing the PA fields

You might need to move the Gantt Chart divider bar to the right to display the fields in the Gantt Chart table. When you click these PERT Analysis toolbar table buttons, you might not see an immediate change in the table data. If this happens, drag the divider bar to the right to display the newly added columns.

After you've entered PERT Analysis figures in the PERT Entry form, you can apply those calculation results to your Entry table by clicking the Calculate PERT button on the PERT Analysis toolbar. If you choose to enter task durations in this way, Office Project 2007 will overwrite any durations and Start or Finish dates you have entered for tasks utilizing the PERT Analysis form.

By default, Office Project 2007 calculates based on the Critical Path Method (CPM), which forecasts the project's total duration by analyzing the least amount of task scheduling flexibility. In project management you can use the PERT Analysis method for estimating task durations and CPM to manage task importance by defining task relationships and constraints. This way, CPM and PERT can work hand-in-hand.

Using the Set PERT Weights button on the PERT Analysis toolbar, you can modify the default weights given to any of the formula variables. However, for the purposes of the certification exam, be sure you understand the default values and use those in any calculations you're asked to perform.

With permission from Microsoft Press, this article content was excerpted from the book, Managing Projects with Microsoft Office Project 2007 (Self-Paced Training Kit for Exam 70-632).