This preview shows page 1. Sign up to view the full content.
Unformatted text preview: t variance-the tendency of variances to cancel one another, the Law of Compensating Error, and the analysis of variances at greater levels of detail when a variance proves to be unacceptable at some summary level control package- applies equally well to schedule variances. But there is another aspect of the schedule variance that needs to be discussed. An acceptable schedule variance at the total project level or at some summary level control package means only that ''overall" the work considered at this level is being accomplished at or better than the planned rate. It does not mean that tasks on the critical path (critical subnet) of the schedule are being accomplished on schedule. We have not yet discussed the meaning of the term "critical path" or its significance. This is covered in Chapter 7. But at this point we can point out that the tasks on the critical path play a role in determining whether or not the project will complete on schedule. Conversely, accomplishing the tasks on the critical path on schedule does not imply that the total work content will ultimately be accomplished as planned. Both the schedule variances and the accomplishment of tasks on the critical path are important measures of project performance with respect to the schedule. The schedule variance is a more global measure of schedule performance, whereas the critical path is a more local measure of schedule performance at any level in the WBS. The critical path can almost always be changed by resequencing the work, whereas the schedule variance is often the measure of a fundamental resource or productivity problem. Page 118 4.3.3— Variance Reporting In this section we discuss the Cost and Schedule Variance Report and two other reports (charts) that are closely related. These are the Cost Performance Trend Chart and the Schedule Performance Trend Chart. These charts are not, strictly speaking, variance reports but are based on related concepts, namely the cost performance ratio and the schedule performance ratio . These concepts are closely related to the concepts of cost variance and schedule variance. We discuss these concepts later in this section. The Cost and Schedule Variance Report is shown in Figure 4-4. It can be produced by clicking on the Cost/Schedule Variance Report button on the Main Menu. This report shows the cost variance and the schedule variance for each control package in the WBS hierarchy. This is the performance report that is of particular interest to the control package managers on large projects. In the old days (when project management systems ran on mainframe computers and project control reports were printed on line printers), the Cost and Schedule Variance Reports usually had page breaks after each control package. This way, the reports could be easily separated so that each control package manager could get the part of the report that corresponded to his or her individual responsibility. Modern Project does not provide thi...
View Full Document
- Spring '10