Analyzing Stability of Estimates at Completion
Results
Stability Analysis Figures 1 and 2 display the average %DCAC for the 27 contract efforts analyzed using EVM and ES metrics. Table 2 summarizes the stability results of Christensen (1996) and Kim et al. (2019). Consistent with Christensen (1996), EAC CPI is a floor estimate of final cost for a majority of the project life cycle. Contrary to Christensen (1996) and Kim et al. (2019), however, EACs calculated using EVM metrics fail to achieve stability within 10% deviation from final cost until approximately 70% complete. Christensen (1996) found EAC CPI to achieve stability within 10% deviation at approximately 50% complete and EAC SPI ($) and EAC SCI ($) to achieve stability within 10% deviation at contract initiation. Kim et al. (2019) found EAC CPI to achieve stability within 10% deviation at approximately 55% complete and EAC SCI ($) to achieve stability within 10% deviation at approximately 50% complete.
FIGURE 1. GRAPHICAL COMPARISON OF PERCENT DEVIATIONS FROM COST AT COMPLETION FOR EAC’S CALCULATED WITH EVM METRICS
EAC Comparison (Earned Value Management)
5%
0%
-5%
-10%
EACcpi EACspi($) EACsci($)
-15%
-20%
-25%
-30%
-35%
-40% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Project Completion
Note. cpi = Cost Performance Index; DCAC = Deviation from Cost at Completion; EAC = Estimate at Completion; EVM = Earned Value Management; sci = Schedule Cost Index; spi = Schedule Performance Index.
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Defense ARJ , Spring 2025, Vol. 32 No. 1
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