Title
Improved Mean and Variance Estimating Formulas for PERT Analyses
Abstract
The program evaluation and review technique (PERT) is a popular method for measuring and controlling activity progress in projects. Its structure is simple, and the result is fairly accurate as long as none of its base assumptions is violated. Many authors have challenged these assumptions and suggested improvements to the mean and variance formulas. This paper quantifies the accuracy of a wide range of PERT mean-variance estimation formulas. In addition, we develop a new PERT variant using common percentiles. The proposed method uses three points for estimation, just like the classical PERT. However, it provides options for the selection of the three points. It provides different set of probability weights by the selection of the three points and what parameter to estimate, i.e., mean or variance, which minimizes the estimation error. We compare the accuracy of our approach with existing methods using the Pearson distribution system. Our use of the Pearson system allows us to systematically compare different PERT methods over a wider range of distribution shapes than has previously been considered. This analysis shows that, despite its simple structure, our new method outperforms existing methods when estimating means and variances of most bell-shaped and J-shaped beta distributions. We also demonstrate how practitioners could use our new methods in actual project settings.
Year
DOI
Venue
2014
10.1109/TEM.2014.2304977
IEEE Trans. Engineering Management
Keywords
Field
DocType
Forecasting/statistics/probability, optimization, project evaluations, project scheduling, scheduling
Schedule (project management),Pearson distribution,Scheduling (computing),Shape of the distribution,Measurement uncertainty,Statistics,Mathematics,Percentile,Program evaluation and review technique,Beta distribution
Journal
Volume
Issue
ISSN
61
2
0018-9391
Citations 
PageRank 
References 
1
0.39
2
Authors
3
Name
Order
Citations
PageRank
Seong Dae Kim1386.30
Robert K. Hammond210.72
J. Eric Bickel311112.96