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Testing Earned Schedule Forecasting Reliability

FEATURED PAPER

Walt Lipke

Oklahoma, USA
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Abstract

Project duration forecasting using Earned Schedule (ES) has been affirmed to be better than other Earned Value Management based methods. Even so, the results from a study, employing simulation techniques, indicated there were conditions in which ES performed poorly. These results have created skepticism as to the reliability of ES forecasting. A recent paper examined the simulation study, concluding through deduction that ES forecasting is considerably better than portrayed. Researchers were challenged to examine this conclusion, by applying simulation methods. This paper uses real data for the examination, providing a compelling argument for the reliability of ES duration forecasting.

Introduction

A research study of project duration forecasting was made several years ago, employing simulation methods applied to created schedules having several variable characteristics (Vanhoucke & Vandevoorde, 2007). The overall result from the study was that forecasts using Earned Schedule (ES), on average, are better than other Earned Value Management (EVM) based methods. However, in certain instances the ES forecast was not.

The scenarios examined in the 2007 study are depicted in figure 1. The scenario model indicates nine possible outcomes. These outcomes are grouped into three categories: true, misleading, and false. True outcomes are associated with reliable forecasts, whereas the misleading and false categories indicate unreliable ES duration forecasting.

The three groupings are more fully explained as follows:

  • The true scenarios (1, 2, 5, 8, 9) have the characteristic that the relationship of the real or final project duration (RD) to the planned duration (PD) can be inferred from the schedule performance efficiency indicator, SPI(t).Using scenario 1 for example, SPI(t) is greater than 1 (indicating good performance), while RD is less than PD (as one would expect from the indicator); i.e., the indicator is consistent with the duration result.
  • The misleading scenarios (4, 6) are characterized by the critical activities being completed as planned, while the non-critical activities are not. The RD equals PD; however, SPI(t) is either greater or less than 1. Thus, the indicator is inconsistent with the duration outcome.
  • The false scenarios (3, 7) occur for two circumstances: 1) When non-critical activity performance is good and critical performance is poor, or 2) When critical activity performance is good and non-critical is poor. For these scenarios, the indicator, SPI(t), infers an outcome in opposition to the actual duration.

As indicated by the model only five of the nine possible outcomes are true (SPI(t) consistent with the final duration). Thus, a negative perception is created as to the reliability of ES forecasting.

More (including figures and footnotes)…

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About the Author

Walt-LipkeWalt Lipkeflag-usa

Oklahoma, USA 

Walt Lipke retired in 2005 as deputy chief of the Software Division at Tinker Air Force Base. He has over 35 years of experience in the development, maintenance, and management of software for automated testing of avionics. During his tenure, the division achieved several software process improvement milestones, including the coveted SEI/IEEE award for Software Process Achievement. Mr. Lipke has published several articles and presented at conferences, internationally, on the benefits of software process improvement and the application of earned value management and statistical methods to software projects. He is the creator of the technique Earned Schedule, which extracts schedule information from earned value data.Mr. Lipke is a graduate of the USA DoD course for Program Managers. He is a professional engineer with a master’s degree in physics, and is a member of the physics honor society, Sigma Pi Sigma (SPS). Lipke achieved distinguished academic honors with the selection to Phi Kappa Phi (FKF). During 2007 Mr. Lipke received the PMI Metrics Specific Interest Group Scholar Award. Also in 2007, he received the PMI Eric Jenett Award for Project Management Excellence for his leadership role and contribution to project management resulting from his creation of the Earned Schedule method. Mr. Lipke was selected for the 2010 Who’s Who in the World.  At the 2013 EVM Europe Conference, he received an award in recognition of the creation of Earned Schedule and its influence on project management, EVM, and schedule performance research. Most recently, the College of Performance Management awarded Mr. Lipke the Driessnack Distinguished Service Award, their highest honor. Walt can be contacted at [email protected].