Critical Path Method CPM

Schedules are developed from task sequences, durations, resource requirements, start dates, and finish dates. Various mathematical methods are used to calculate project schedules.

The Critical Path Method, or CPM, is the technique that underlies Microsoft Office Project 2003 scheduling. The focus of CPM is to analyze all series of linked tasks in a project and determine which series has the least amount of scheduling flexibility; that is, the least amount of slack. This series becomes designated as the critical path.

Four date values are part of the slack calculation for each task:

The difference between the late start and early start dates is compared, as is the differ ence between late finish and early finish. The smaller of the two differences becomes the value for total slack.

Viewing the Critical Path

The easiest way to see the critical path in a Gantt chart is to click View, Tracking Gantt. The Tracking Gantt highlights the critical path in red in the chart portion of the view (see Figure 9-4). The Entry table is applied by default to the Tracking Gantt, just as in the regular Gantt Chart.

Critical path

Critical path

Noncritical paths

Figure 9-4. The Tracking Gantt highlights the critical path.

Noncritical paths

Figure 9-4. The Tracking Gantt highlights the critical path.

Go To Selected Task

Tip Move the Gantt chart to the selected task

When you first open a Gantt chart, the timescale is at today's date. If the tasks you're reviewing are in the past or future, you might not see the Gantt bars in the chart. Click a task whose Gantt bar you want to see. On the Standard toolbar, click Go To Selected Task.

Go To Selected Task

You can also use the Gantt Chart Wizard, which formats the chart portion of any Gantt Chart view to highlight the critical path. To do this, follow these steps:

Gantt Chart Wizard

Click View, Gantt Chart.

If you want to modify another Gantt Chart view, such as the Leveling Gantt or Tracking Gantt, display that view instead.

On the Formatting toolbar, click Gantt Chart Wizard.

On the first page of the Gantt Chart Wizard, click Next.

On the second page, select the Critical Path option (see Figure 9-5). Then click Next.

Figure 9-5. To highlight the critical path Gantt bars, select the Critical Path option.

5 On the third page, select the option for any text you want to accompany the Gantt bars, such as resource names, dates, and so on. Click Next.

6 On the fourth page, select whether you want the link lines for task dependencies to show. Click Next.

7 On the final page, click the Format It button.

Microsoft Project 2003 formats your Gantt Chart according to your specifications.

8 Click the Exit Wizard button to view your new Gantt Chart format, which displays red Gantt bars for critical tasks (see Figure 9-6).

Figure 9-6. Use the Gantt Chart Wizard to instantly highlight critical path tasks in any Gantt o Chart view.

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Figure 9-6. Use the Gantt Chart Wizard to instantly highlight critical path tasks in any Gantt o Chart view.

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The Gantt Chart Wizard is convenient for quickly changing the Gantt bar format of certain types of tasks. However, if you use the wizard to do your formatting, you might lose certain standard Gantt bar formatting that you want to preserve. For example, the Deadline bar style is lost.

If you want to see only critical tasks in a Gantt Chart view, switch to the Detail Gantt or Tracking Gantt.

If you want to highlight critical tasks in the Gantt Chart, customize the bar styles.

For more information, see "Formatting a Gantt Chart View" on page 766.

Although displaying the Detail Gantt or using the Gantt Chart Wizard can display the Gantt bars for the critical path at a glance, you can also look at the details for individual critical tasks. The following list details different methods for viewing critical tasks:

Display the Detail Gantt. Click View, More Views, Detail Gantt. This view shows the critical path tasks in red Gantt bars (see Figure 9-7). By default, the Delay table is applied to the sheet portion of the view.

Critical path

Slack

Figure 9-7. The Detail Gantt shows the critical path as well as available slack.

Critical path

Slack

Figure 9-7. The Detail Gantt shows the critical path as well as available slack.

Review the Critical Tasks report. Click View, Reports. Double-click Overview, and then double-click Critical Tasks. Group tasks by critical and noncritical tasks. Click Project, Group By, Critical (see Figure 9-8). To return tasks to their original order, click Project, Group By, No Group. You can also use the Group By tool on the Standard toolbar.

Group By

Task Name

Wed 4/7*04 Fri 4/16i04

E Critical: No 52 days Mon 3/8/04 Tue 5/18/04

Identify costs for new office (chairs, desks, equipment) 10 days Mon 3/8*04 Fri 3/i9/04

Prepare a budget for the move 12 days

Select the move day 7 days

Hire contractors for major tenant improvements 6 days

Obtain necessary permits 7 days

Evaluate phone system needs 10 days

Order new phone number 14 days

Order new fax number 16 days

Communicate to employees 12 days Mon 5/3*04 Tue 5/18/04

E Critical: Yes 71 days Mon 3/8/04 Mon 6/14/04

Make list of key needs that must be met by new office space 7 days Mon 3/8*04 Tue 3/16/04 Identify potential office sites

Make final decision on office space 11 days Wed 4/14/04 Wed 4/28/04

Finalize lease on office space 12 days Thu 4/29*04 Fri 5/14/04 Identify major tenant improvement needs Obtain estimates from contractors for major tenant improvements

Figure 9-8. Use the Critical grouping to group critical tasks together and noncritical tasks together.

Filter

Filter for critical tasks. Click Project, Filtered For, Critical. Only critical tasks are shown. To show all tasks again, click Project, Filtered For, All Tasks. You can also use the Filter tool on the Formatting toolbar.

Report

Use the Project Guide. On the Project Guide toolbar, click Report. Click the See The

Project's Critical Tasks link. The view changes to a Critical Tasks Gantt generated by the Project Guide. Additional information is provided in the Project Guide side pane.

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