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Forecasting Schedule Variance Using Earned Schedule

FEATURED PAPER

By Walt Lipke

Oklahoma, USA


Abstract

The application of Earned Value Management (EVM) provides insight to a project’s performance, thereby providing management information useful for project control. Many projects, especially those that are large, establish milestones in their schedules. Milestones are used to assess progress, usually by evaluation of product characteristics, at an interim point significant to the project. Although EVM plays a role, the method is not focused on milestone achievement. To address this perceived void, this paper introduces an Earned Schedule method for determining, in process, the achievability of a specific milestone.      

Introduction

EVM and ES provide management information about current performance; i.e., performance efficiency and variance from the cost and time estimates comprising the project’s performance baseline. As well, the two methods are used to forecast the cost and duration at project completion. EVM and ES are oftentimes applied to components of a large project to provide more management granularity. The categories of management information, derived for project components, are identical to the total project; i.e., performance efficiency, variance, and end-point forecasts. In this mode, the EVM/ES approach does not provide an assessment regarding achievement of a project milestone.1

Assessing milestone achievement through the application of EVM and ES is somewhat of a mind-twist. The assessment desired is different from their current use. That is, it is not for present or past status periods, nor for project completion. Rather, the analysis interest, the milestone, is scheduled at a time in-between the two. This difference is significant and raises the question:

Using EVM/ES methods, is assessment of milestone achievability possible?

Describing the approach, the calculations, and methods is the goal of this paper. Hopefully, by the conclusion the answer will be recognized, “Yes, it can be done.”

Earned Schedule Review

Earned Schedule is dependent upon EVM; the ES measure is derived from the accrued earned value (EV) and the performance measurement baseline (PMB) [Lipke, 2003]. As shown in figure 1, “the idea is to determine the time at which the EV accrued should have occurred.” The time duration from project start to the point on the PMB where the planned value (PV) equals the EV accrued is the earned portion of the planned duration (PD), i.e. ES.

As diagrammed in the figure, determining the value of ES is a simple matter of interpreting the graph. In practice, however, a calculation method is applied. Its description is explained, in detail, in the Earned Schedule book [Lipke, 2009]. As well, to simplify and encourage usage the ES Calculator spreadsheet is freely downloadable from the ES website.2 Additionally, commercial EVM tools provide ES analysis capability.

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About the Author


Walt Lipke

Oklahoma, USA

 

 

Walt Lipke retired in 2005 as deputy chief of the Software Division at Tinker Air Force Base, where he led the organization to the 1999 SEI/IEEE award for Software Process Achievement. He is the creator of the Earned Schedule technique, which extracts schedule information from earned value data.

Credentials & Honors:

  • Master of Science – Physics
  • Licensed Professional Engineer
  • Graduate of DOD Program Management Course
  • Physics honor society – Sigma Pi Sigma (SPS)
  • Academic honors – Phi Kappa Phi (FKF)
  • PMI Metrics SIG Scholar Award (2007)
  • PMI Eric Jenett Award (2007)
  • EVM Europe Award (2013)
  • CPM Driessnack Award (2014)

Mr. Lipke can be contacted at [email protected]

To view other works by Walt Lipke, visit his author showcase in the PM World Library at http://pmworldlibrary.net/authors/walt-lipke/