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Fine-Tuning Task Details in Microsoft Project 2010

Viewing the Project’s Critical Path

A critical path is the series of tasks that will push out the project’s end date if the tasks are delayed. The word critical in this context has nothing to do with how important these tasks are to the overall project. It refers only to how their scheduling will affect the project’s finish date; however, the project finish date is of great importance in most projects. If you want to shorten the duration of a project to bring in the finish date, you must begin by shortening (also referred to as crashing) the critical path.

Over the life of a project, the project’s critical path is likely to change from time to time as tasks are completed ahead of or behind schedule. Schedule changes, such as changing task relationships or durations, can also alter the critical path. After a task on the critical path is completed, it is no longer critical because it cannot affect the project finish date. In Chapter 14, “Getting Your Project Back on Track,” you will work with a variety of techniques to shorten a project’s overall duration.

A key to understanding the critical path is to understand slack, also known as float. There are two types of slack: free and total. Free slack is the amount of time a task can be delayed before it delays another task. Total slack is the amount of time a task can be delayed before it delays the completion of the project.

A task is on the critical path if its total slack is less than a certain amount—by default, if it is zero days. In contrast, noncritical tasks have slack, meaning they can start or finish earlier or later within their slack time without affecting the completion date of a project. One way to see the critical path is to switch to the Detail Gantt view.

In this exercise, you view the project’s critical path.

  1. On the View tab, in the Task Views group, click the down arrow below the Gantt Chart button and then click More Views.

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  2. In the More Views dialog box, select Detail Gantt, and then click Apply.

    The project appears in the Detail Gantt view.

  3. On the View tab, in the Zoom group, click Entire Project.

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    Because of the highly sequential nature of the task relationships in this project plan, almost all the tasks are on the critical path, and in the Detail Gantt view, their Gantt bars are formatted in red.

    Notice the Gantt bar of task 41, Review with author. The blue bar represents the duration of the task. The thin teal line and the number next to it represent free slack for this task. As you can see, this particular task has some slack and is therefore a noncritical task. (Remember that the term critical in this sense has nothing to do with the task’s importance, but only with how much or little total slack is associated with the task—and, ultimately, what effect the task has on the project’s finish date.)

  4. On the View tab, in the Task Views group, click the down arrow below the Gantt Chart button and then click Gantt Chart.

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    Working with the critical path is the most important way to manage a project’s overall duration. In later exercises, you will make adjustments that might extend the project’s duration. Checking the project’s critical path and, when necessary, shortening the overall project duration are important project management skills.

Here are a few other things to keep in mind when working with the critical path:

  • By default, Project defines a task as critical if it has zero slack. However, you can change the amount of slack required for a task to be considered critical. You might do this, for example, if you wanted to more easily identify tasks that were within one or two days of affecting the project’s finish date. On the File tab, click Options, and in the Project Options dialog box, click the Advanced tab. In the Tasks Are Critical If Slack Is Less Than Or Equal To box, enter the number of days you want. In this same dialog box, you can elect to display multiple critical paths.

  • Project constantly recalculates the critical path even if you never display it.

  • You see free slack represented in the chart portion of the Detail Gantt view, and you can also see the values of free and total slack in the Schedule table. You can apply the Schedule table to any Gantt Chart or Task Sheet view.

  • You can toggle the formatting of critical tasks and slack directly in any Gantt Chart view. On the Format tab, in the Bar Styles group, select or clear the Critical Tasks and Slack check boxes.