Critical Path

All projects have tasks that must be completed on schedule for the project to finish on time, if the task is delayed, the project completion date might also be delayed these tasks are called Critical Tasks. A series of Critical Tasks makes up a project’s Critical Path (displayed in red) in plan example.

The amount of time that a task can slip before it affects another task or the project’s finish date is called Slack. Free slack is how much a task can slip before it delays another task.  Total slack (or float) is the amount of time a task can slip before it delays the project and it therefore drives the finish date of the project.

If it’s important for your project to finish on schedule, pay close attention to the tasks on the critical path and the resources assigned to them.

If a critical task takes longer than expected or a resource is suddenly unavailable for a critical task, the project will not be completed by the original finish date.

A series of tasks is generally interrelated by task dependencies.

Remember the four task dependencies:

  • Finish-to-start [FS]
  • Start-to-start [SS]
  • Finish-to-finish [FF]
  • Start-to-finish [SF]

Although there are likely to be many series of interrelated tasks in your project plan, the series of tasks that will finish the latest is the project’s critical path. The critical path can change as critical tasks are completed or as tasks in another series of tasks are delayed and your project plan will need updated.

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