From the course: Project Management Foundations

Understand the critical path

From the course: Project Management Foundations

Understand the critical path

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- The critical path is the longest sequence of tasks in your schedule. Why is the critical path so critical? Because any delay on that path delays the finished date of the project. Just as important. If you can figure out how to shorten the critical path, you can shorten the project schedule. How do you tell which tasks are on the critical path? Simple. They don't have any slack, also known as float. Just like a string with no slack. Critical tasks can't move without affecting the project finished date. In this simple example, the system and training tasks occur one after the other with no slack. If any of these tasks are delayed, the project finished date moves later in time. On the other hand, if a task has slack like the reports task here, it can start later without delaying the tasks that come after it. The reports task could delay by a few weeks before it delays the project finish. Let's look at how you tell whether or not a task has slack. A task has two sets of start and finish dates. The early start and early finish are the earliest possible dates the task can start or finish based on its dependencies with other tasks. You calculate these with what's called a forward pass. That's where you start at the project start date and use task durations and dependencies to calculate when they finish. For example, the reports task can start as early as October 26th and finish on November 27th. The late start and late finish are the latest possible dates without delaying tasks that follow. You calculate these dates by working backwards from the end of the project. You got it. The backward pass. The late finish for the reports task is December 18th, so working backwards, the late start is November 16th. The task has several weeks of slack so it isn't on the critical path. Critical tasks have no slack. In other words, the early and late dates are the same. That's why the training task is on the critical path. The good news, you don't have to perform these calculations. When you use project scheduling programs, they calculate the critical path for you. The critical path is the place to look when you want to keep your project on time or deliver it early. To test your understanding, calculate the late dates for the tasks and the exercise and use them to identify the critical path.

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