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Do Not Sum Earned-Value-Based WBS-Element Estimates-at-Completion

CEBok Reference Track

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EACsare Random Variables, Not Deterministic Numbers, and Must be Handled Statistically
–Avoid Meaningless, Contradictory Outcome of Roll-up Procedure
–Get Mean, Median, Mode of Total-System Cost at Completion, as well as All Cost-at-Completion Percentiles
•EAC Uncertainty is Due to
–Discrepancies Among CPI-, SPI-, WTAVG-, and SCI-Based Methods of Calculating EACs
–Differences Between Total-Program EACsCalculated by Roll-up of WBS-Element EACsand Directly from Total-Program EV Data
•Coherent Theory Presented Here to Take These Facts into Account when Estimating Total-Program EAC


Stephen A. Book

The Aerospace Corporation