Schedule Updating and Project Control - Construction Project Scheduling and Control - page 202

Earned Value versus CPM
It is important to note that EV analysis and schedule updating may yield conflicting
results. The schedule variance (SV) may be positive, but the schedule update shows
that the project is behind, or vice versa. This situation occurs mainly because the EV
analysis is cost-driven even for calculating schedule variance, whereas schedule updat-
ing focuses on the critical path, without regard to monetary issues. For example, the
contractor may get a positive schedule variance in earned value analysis by completing
noncritical activities ahead of schedule while the critical path may be behind. CPM
still gives the most accurate readings on whether the project is ahead of or behind
schedule. Several authors have suggested schedule variance (SV) that is time-based
with several approaches 14 Such suggestions are beyond the scope of this topic.
SCurves
Earned value (BCWP) and actual cost (ACWP) may be plotted against the baseline
(BCWS), as shown in Figure 7.19. Both curves, representing the ACWP and the
BCWP, are usually extrapolated to forecast the estimate at completion (EAC) and
the date of completion.
EV Analysis at Different Levels When using the WBS, project managers may
look at work at different summary levels.
Figure 7.19 Earned value (budgeted cost for work performed, or BCWP) and actual cost
(actual cost for work performed, or ACWP) plotted against the baseline (budgeted cost for
work scheduled, or BCWS)
14 Warburton and Kanabar (2008), Anbari (2003).