Trend Analysis
Trend analysis involves collecting schedule measurement data during each status period and plotting them over time. Sustained variances in one direction should be documented to assess whether the program is heading toward a problem and to determine whether action is necessary. Trend analysis provides valuable information about how a program is performing. Knowing what has caused problems in the past can help determine whether they will continue. Typical schedule measure data that can help managers know what is happening in their programs are
comparisons of the cumulative number of completed activities to the cumulative number of baselined activities planned to be completed;
comparisons of the cumulative number of activities forecasted to be completed to the number of baselined activities planned to be completed;
available resources over time, highlighting overallocations;
total float and schedule contingency tracked by status period;
comparisons of actual, forecasted, and baselined completed activities.
The use of total float over time is a key measure for monitoring the health of the program. A quick draw down of total float early in the program may indicate that more serious schedule delays and cost overruns will occur in the future.
Comparisons of actual, forecasted, and baselined completed activities are useful for identifying unrealistic peaks of activity. Peaks of activity will have to be completed at a higher rate than the rate at which activities have previously completed. For example, if on average 15 detail activities have been accomplished per 2-week period yet forecasts imply that 30 detail activities need to be completed every 2 weeks to finish on time, the schedule is most likely unrealistic.
A measure known as the baseline execution index (BEI) is commonly used in baseline analyses. It is the ratio of the number of detail activities that were completed to the number of detail activities that should have been completed by the status date. A BEI of 1 indicates that the project is performing according to plan. A BEI less than 1 indicates that, in general, fewer activities are being completed than planned; a BEI greater than 1 indicates that, in general, more activities are being completed than planned.
The BEI is an objective measure of overall schedule efficiency because it compares actual completions to planned completions. However, it is a summary measure—that is, it does not provide insight into why activities are not being completed according to plan or take into account the importance of their not being completed according to plan. For example, delayed activities that are on the critical path or on near-critical paths are given weight equal to delayed activities that have free float available.
To provide additional insight, the BEI can be calculated against any group of activities—WBS level, resource group, or activity duration. It can also be calculated for different periods of time—for example, from the start of the program through the status date or for the most recent reporting period. The BEI is always 1 at the end of a project if, eventually, all activities are completed. Finally, if contingency activities are included in the schedule network, their durations should be zeroed out before calculating the BEI. Including contingency activities can artificially lower the BEI because they have no actual start or finish dates.