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Ask the Experts: Define Critical

Q: I have a very important task that my boss thinks is critical to the project outcome, and it is not showing up as red. How can I make it critical?

A: A bit of history reveals that project management of a sort has been around since humans began thinking. I’m sure the pyramids had a project manager to mastermind the completion of the critical tasks. (Whether they were produced within cost is debatable, though they seem to have been finished on time!) The discipline of what is generally known as Network Analysis began in the early 1950s in Europe, with the development of Critical Path Method and project network techniques, as well as others. In the United States, with the development of the Polaris missile system evolved the technique called Program Evaluation and Review Technique or PERT.

These tools allowed a project manager to define a series of tasks that were essential for achieving the product, link the tasks in a logical pattern to form a network, and analyze individual task timings to calculate the critical path to achieve an end date. Thus, Network Analysis is the core technique of all modern project management practices, and working with Microsoft Project is no exception.

In essence, if you have three tasks, task A taking 5 days, and B and C of 3 days each, all starting on a Monday, then the critical task is the one that takes the longest: A, which requires five days.

Figure 1. The critical task is the one that’s the longest, in this case, A.

Ask the Experts: Define Critical

Looking at Figure 1, we can see that B and C have some slack. They could each be started two days later without affecting the end date. A has none. However, if task C can’t be started until Task B has finished (you cant put a roof on until the walls are erected), then we have to link task C to follow task B. The duration of the combination of B followed by C is now six days, making it the longest time path — and therefore critical. Tasks B and C are both critical with zero slack, and the path through B and C is the Critical Path.

Figure 2. Linking task B to task C now makes that combination critical.

Ask the Experts: Define Critical

Thus, it’s important that you understand the principles of project planning before applying them to a project management software package like Microsoft Project. The term critical has a specific meaning within project management to mean an activity with zero slack. The actual importance to the boss or the organization has nothing to do with whether it is critical or not; only the arithmetic determines criticality. I wrote an introductory guide to network analysis some years ago and have attached this to the Project MVP website. Follow through the example diligently, making sure you understand the arithmetic as you go along. (It’s only adding and subtracting!) It will help you understand the technique of listing tasks, linking them, adding durations, and calculating the critical path.

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