Critical path and slack

The critical path marks the series of tasks in a project that must be completed on time for the overall project to stay on schedule. For example, suppose that you are planning a going-away party at your office. You have three days to plan the party. The following table lists some of the tasks that are involved and indicates their time frames.



Signing the good-bye card

three days

Ordering food

one day

Reserving a room

one hour

Buying a good-bye gift

one day

The shortest task, reserving a room, takes only one hour. Assuming that plenty of rooms are available for holding the party, you can delay reserving the room until the last hour of the third day. Delaying this task doesn't cause any delay in holding the party — as long as you accomplish this task by the end of the longest task, which is getting everyone to sign the good-bye card. Therefore, the task of reserving a room isn't on the critical path. However, you can't delay the task of signing the good-bye card, which is projected to take three days to accomplish, without delaying the party. Therefore, the card-signing task is on the critical path. (Of course, this example is very simple; typically, a whole series of tasks that can't afford delay form an entire critical path.)

The following points further define and clarify these concepts:

♦ The critical path changes as the project progresses. Remember that a critical path is a means of identifying tasks that have no leeway in their timing to ensure that they don't run late and affect your overall schedule. Knowing where your critical path tasks are at any point during the project is crucial to staying on track. Figures 1-1 and 1-2 show the same schedule — first with all tasks displayed and then filtered to show only the tasks that are on the critical path.

Figure 1-1: Tasks with slack displayed alongside those on the critical path.

- Cross- See Chapter 7 to find out how to filter for only critical tasks and to see more infor-

| Reference.mation about changing the view of your project.

♦ Slack, also called float, is the amount of time that you can delay a task before that task moves onto the critical path. In the preceding example, the one-hour-long task — reserving a room — has slack. This task can slip a few hours, even a couple of days, and the party will still happen on time. However, if you wait until the last half-hour of the third day to reserve a room, that task will have used up its slack and it then moves onto the critical path.

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Project Management Made Easy

Project Management Made Easy

What you need to know about… Project Management Made Easy! Project management consists of more than just a large building project and can encompass small projects as well. No matter what the size of your project, you need to have some sort of project management. How you manage your project has everything to do with its outcome.

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