A scenario is presented in which current variances are seen as typical. Here are the figures:
PV=800, BAC=700, EV=675, AC=750.
Correct Answer: C
With the following
Explanation:
EAC = [AC + (BAC - EV) / .9] = 861.11 or 861 rounded down.[#1] In order to get this answer, you have to ADD the remaining budget (BAC - EV) to AC and THEN divide the sum by CPI. But that's contrary to what the parentheses indicate in PMBOK, that is: EAC = AC + ((BAC - EV)/CPI). Now, if you were to obey the order of operation implied in PMBOK, you'd come up with 777.77 or 778 rounded up, which is answer A. So which one is it - 778 or 861?[#2] Actually, even though the formulas have a different meaning based on the context, mathematically they are the same: EAC = BAC / CPI with no variance EAC = AC + ( BAC - EV ) / CPI with variance, based on performance But, CPI = EV / AC, so EAC = AC + ( BAC - EV ) / CPI = AC + BAC / CPI - EV / CPI = AC + BAC / CPI - EV / ( EV / AC ) = AC + BAC / CPI - EV * ( AC / EV ) = AC + BAC / CPI - AC = BAC / CPI
Why does this work? When there is no variance, the CPI should be 1, and the EAC should be the BAC.[#3] Forget about all that and just use BAC / CPI (see derivation below):700 /
0.9 = 778.You are right, the book is wrong.