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CUMAV or Unit?
Is Cum Average vs. Unit Theory a Fair Fight?

Analysis Track

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The statistics of the regressions used to judge significance and “best fit” are inherently biased towards Cum Average because the Cum Average metric is smoothed by the very fact that it is cumulative. This paper will use generated data with and without error terms in an attempt to show the degree of this bias and will seek to generate some thumb rules or some insight to help the analyst decide between the two models.

It has long puzzled the authors as to whether both learning models can be true, and why most practitioners in some commodities, and some practitioners in most commodities lean more toward the one than the other. It would be a grand project indeed to decide whether the one model or the other is best either globally or locally. The scope of that endeavor is, however, too great. In lieu of that project, we hope that by shedding light on this puzzling problem we can enable all practitioners to decide whether their preference is rational, and perhaps thereby bring some rigor to this problem.


Bethia Cullis
Bethia L. Cullis is an Operations Research Analyst at Northrop Grumman IT. She is currently the Section Manager for the C101 section and the Program Manager for all Independent Cost Evaluations (ICEs) required by NGIT, NGNN, NGSS and NGTS. In addition to her ICE work, Ms. Cullis has supported numerous ship programs including DD(X), the DDG 51 class, LHD 8 and LHA 6, the LPD 17 class and CVN 21. She is the lead or co-author of three professional papers, all of which were presented at the SCEA 2007 conference and one of which was presented at the Naval Postgraduate School’s Acquisition Research Symposium. For the past two years she has taught at the SCEA national conference. Before joining Northrop Grumman in 2004, Ms. Cullis completed her undergraduate degree in Economics and English at Case Western Reserve University. She also worked as an analyst for Newry Corporation, a competitive consulting firm in Cleveland, OH.

Richard Coleman
Richard L. Coleman is a 1968 Naval Academy graduate, received an M. S. with Distinction from the U. S. Naval Postgraduate School and retired from active duty as a Captain, USN, in 1993. His service included tours as Commanding Officer of USS Dewey (DDG 45), and as Director, Naval Center for Cost Analysis. He has worked extensively in cost, CAIV, and risk for the Missile Defence Agency (MDA), Navy ARO, the intelligence community, NAVAIR, and the DD(X) Design Agent team. He has supported numerous ship programs including DD(X), the DDG 51 class, Deepwater, LHD 8 and LHA 6, the LPD 17 class, Virginia class submarines, CNN 77, and CVN 21. He is the Director of the Cost and Price Analysis Center of Excellence and conducts Independent Cost Evaluations on Northrop Grumman programs. He has more than 65 professional papers to his credit, including five ISPA/SCEA and SCEA Best Paper Awards and two ADoDCAS Outstanding Contributed Papers. He was a senior reviewer for all the SCEA CostPROF modules and lead author of the Risk Module. He has served as Regional and National Vice President of SCEA and is currently a Board Member.

Peter Braxton
Peter J. Braxton holds an AB in Mathematics from Princeton University and an M.S. in Applied Science (Operations Research) from the College of William and Mary.
He has worked to advance the state of knowledge of cost estimating, Cost As an Independent Variable (CAIV), Target Costing, and risk analysis on behalf of the Navy Acquisition Reform Office (ARO), the DD(X) development program, and other ship and intelligence community programs. He has co-authored several professional papers, including ISPA/SCEA International Conference award-winners in CAIV (1999) and Management (2005). He served as managing editor for the original development of the acclaimed Cost Programmed Review Of Fundamentals (CostPROF) body of knowledge and training course materials and is currently undertaking to lead a large team of cost professional in a comprehensive update thereof. He serves as SCEA’s Director of Training, a Northrop Grumman Technical Fellow, and Director of Research within TASC’s Management Consulting Division. He was named SCEA’s 2007 Estimator of the Year for contributions in Education.

Jacquelyn McQueston
Jacquelyn T. McQueston graduated from the College of William and Mary in 2007 with a M.S. in Computer Science, with a concentration in Computational Operations Research. She also holds a B.S. in Mathematics from the College of William and Mary with a concentration in Probability and Statistics. She joined Northrop Grumman as an Operations Researcher in June 2007 and performs cost analysis for the Intelligence Community. She also works on a team conducting Independent Cost Proposal Evaluations throughout Northrop Grumman.