# Critical Tasks: The Tasks That Make a Difference

When you want to shorten your project schedule, where do you begin? You begin by examining your project’s critical tasks, the tasks that must finish on time for the entire project to finish on time. The project plan’s critical path is the sequence of tasks that ends on the latest finish date. The finish date of the last task in the critical path is the project finish date.

By default, a critical task has zero total slack time, which is the amount of time a task can slip before it delays the project finish date. If any critical task slips, the project finish date will likely slip as well.

Critical tasks are like stacked sections of a column holding up a roof. The column is the critical path, and the roof represents the project finish date. Noncritical tasks are like decorative columns that are lower than the roof. To raise or lower the roof, you adjust the height of the "critical" column.

If you increase the height of a column of noncritical tasks so that the roof rests on it instead, then that column becomes "critical." The original column of critical tasks becomes "noncritical."

Microsoft Project recalculates the critical path every time you change task data. A critical task may become noncritical and a noncritical task may become critical as you assign resources, change links, and so on.

Decreasing the duration of a noncritical task has no effect on the project end date.

You can experiment with your project plan by altering one critical task at a time. Change one element of a critical task to see how the change affects the schedule as a whole. For example, you can reduce a task’s duration to see if that change causes the project to end sooner. Or, if a resource assigned to work on two concurrent tasks becomes overworked, you can reschedule one of those tasks.

But don’t start altering critical tasks to fine-tune your schedule until you can distinguish critical tasks from noncritical ones. Microsoft Project provides several ways for you to display critical tasks and focus on the ones to which you should give the most attention.

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