How to Keep IT Projects on Schedule, Part 2: PERT Charts

By Mike Foster

[Editor’s note: In Part 1 of this series, we explored some of the more basic project management tools available to and for IT professionals: the WBS system and the Gantt chart. Read Part 1 here.]

Moving on to more advanced realms of IT project management brings is to the PERT chart.

What is it? A PERT chart will show which steps in an IT project cannot be delayed without delaying the entire project.

The last two blog entries were about IT professionals creating a simple Work Breakdown Structure and a calendar representation called a Gantt chart. The whole point of project management is to help IT keep projects on track. Just as importantly, if the project experiences a delay, IT will be able to give you an updated project completion date.

In this case, a diagram is worth a thousand words, so please look at these examples:

The simplest form of a PERT chart is a circle for each step, containing the name of the step and the estimated duration. Draw arrows that connect the paths related to dependencies, such as:

  • “This step must finish prior to the next step starting;”
  • “This step can start at the same time as another step;” and
  • “Both of these steps must complete before the next step starts.”

Certainly the most useful part of a PERT chart — to me, anyway — is that you can identify the critical path. To find the critical path, first identify how many paths you can take from the start to the finish. Then, for each path, add up the duration of the steps.

If there are four paths, you may end up with durations of, for example:

  • Path 1 duration: 12 days (Task 1’s duration, plus task 3’s duration)
  • Path 2 duration: 11 days (Task 2’s plus Task 3’s durations)
  • Path 3 duration: 10 days (Task 4’s duration)

In this case, Path 1 is the critical path because if there is any delay at all in path 1, the entire project will be delayed. The other paths contain slack time so they can experience delays if necessary.

Mike Foster, CISA, CISSP, is the founder and CEO of Foster Institute. He is a technology expert, author and professional speaker with more than 1,000 presentations under his belt. Mike is author of The Secure CEO: How to Protect Your Computer Systems, Your Company, and Your Job and is regularly sought for interviews and business publication features. He’s been interviewed by USA Today, Forbes Magazine, and The New York Times, as well as many others.

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