Linear Methods for Estimating Schedule Time Earned: Theory and Application

Abstract

This study introduces the term earned time (ET) for the class of linear methods which estimate the amount of project schedule time earned. Existing methods such as planned value (PV) rate, earned duration, and earned schedule are shown to be specific cases of earned time that use different linear rates to convert schedule variance in units of cost to units of time. An additional PV segment method is proposed that uses the linear rate of only the segment of the PV curve responsible for the schedule variance. The ET methods are examined theoretically and applied to three example projects to clarify their underlying assumptions. Five factors are found to guide the selection of a method for a given application: linearity, adherency, parallelism, stage, and status. The study contributes to theory by generalizing the concept of earned time and providing a new method for its estimation. The study is useful for practitioners seeking to apply ET methods and interpret their results.