From the course: Project Management Foundations: Schedules

Too many or too few critical tasks - Microsoft Project Tutorial

From the course: Project Management Foundations: Schedules

Too many or too few critical tasks

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- [Instructor] Critical activities by definition have zero slack. However, slack calculations can be thrown off by several factors in your schedule. As you may already know, you should not use date constraints in your schedule unless absolutely necessary because they limit schedule flexibility. Here's another reason, they affect total slack calculations. Say the project manager adds a finish no later than date constraint to the project complete milestone, because that's when the stakeholders say they want the project done. Because of that date constraint, several tasks in the schedule finish later than the project complete milestone, which makes their total slack negative. If your scheduling program sets activities with zero or negative slack as critical, your schedule might have more critical activities than it should, and that makes it difficult to see which activities are truly critical. The solution to this issue is to focus on the activities that have the smallest values. In this case negative 10 days instead of zero days. If you can set the critical threshold in your scheduling program, change that setting to the lowest total slack value in your schedule, such as minus 10 days. That way activities with slack greater than minus 10 will become non-critical. On the other hand, you might see gaps in your schedule's critical path. In this situation, start by reviewing dependencies between activities to ensure that you have fully defined your project's schedule logic. Date constraints can also create gaps. For example, if you set a date constraint for when a subcontractor delivers a component. Resource calendars might create critical path gaps if resources aren't available when activities are scheduled. In this example, the copy editor isn't available when the copy edit task is scheduled. Because that activity delayed to when the person is available, all the activities before it now have positive total slack and show up as non-critical. When the critical path includes gaps, you must analyze the schedule to determine whether a gap is appropriate. For example, if resource unavailability creates a gap, the slack in the schedule is real and should remain. That is, unless you can find a different resource to perform the work. To determine which activities are the most critical, you look for the ones with the smallest amount of total slack. In this example, the smallest total slack is now two days. So any activities with slack of two days or less are critical. If you can adjust the threshold for critical activities in your scheduling program, adjust that setting to the smallest total slack in your schedule. That way your critical path will be complete once more. These are techniques you can use to correct your critical path if your schedule has too many or too few critical activities.

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