A Probabilistic Method for Predicting Software Code Growth

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A Probabilistic Method for Predicting Software Code Growth

Journal of Cost Analysis and Parametrics

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A significant challenge that many cost analysts and project managers face is predicting by how much their initial estimates of software development cost and schedule will change over the lifecycle of the project. Examination of currently-accepted software cost, schedule, and defect estimation algorithms reveals a common acknowledgment that estimated software size is the single most influential independent variable. Unfortunately, the most important business decisions about a software project are made at its beginning, the time when most estimating is done, and coincidentally the time of minimum knowledge, maximum uncertainty, and hysterical optimism. This article describes a model and methodology that provides probabilistic growth adjustment to single-point Technical Baseline Estimates of Delivered Source Lines of Code, for both new software and pre-existing reused soft-ware that is sensitive to the maturity of their single-point estimates. The model is based on Software Resources Data Report data collected by the U.S. Air Force and has been used as part of the basis for several USAF program office estimates and independent cost estimates. It provides an alternative to other software code growth methodologies, such as Holchin’s and Jensen’s code growth matrices.


Michael A. Ross has over 35 years of experience in software engineering as a developer, manager, process expert, consultant, instructor, and award-winning international speaker. Mr. Ross is currently a Technical Expert for Tecolote Research, Inc. Mr. Ross previous experience includes three years as President and CEO of r2Estimating, LLC (makers of the r2Estimator software estimation tool), three years as Chief Scientist of Galorath Inc. (makers of the SEER suite of estimation tools), seven years with Quantitative Software Management, Inc. (makers of the SLIM suite of software estimating tools) where he was a senior consultant and Vice President of Education Services, and 17 years with Honeywell Air Transport Systems (formerly Sperry Flight Systems) and two years with Tracor Aerospace where he developed and/or managed the development of real-time embedded software for various military and commercial avionics systems. Mr. Ross is a Life Member of ISPA, is currently on the Board of Directors of its Southern California chapter, and regularly presents papers at ISPA/SCEA annual conferences (four of which have been recognized with Best Paper Awards). Mr. Ross did his undergraduate work at the United States Air Force Academy and Arizona State University, receiving a Bachelor of Science in Computer Engineering.