Using robust statistical methodology to evaluate the performance of project delivery systems: A case study of horizontal construction

Abstract

The objective of this study is to demonstrate the application of the bootstrapping M-estimator (a robust Analysis of Variance, ANOVA) to test the null hypotheses of means equality among the cost and schedule performance of the three project delivery systems (PDS). A statistical planned contrast methodology is utilized after the robust ANOVA analysis to further determine where the differences of the means lie.

The results of this research concluded that traditional PDS (Design-Bid-Build, DBB) outperformed the two alternative PDS (“Design-Build (DB) and Construction Manager/General Contractor (CMGC)”), DBB and CMGC outperformed DB, and DBB outperformed CMGC, for the Cost Growth and the Change Order Cost Factor performance. On the other hand, alternative PDS (“DB & CMGC”) outperformed DBB, DB and CMGC (separately) outperformed DBB, and between the two alternative PDS, CMGC outperformed DB, for the Schedule Cost Growth performance.

These findings can help decision makers/owners making an informed decision, regarding cost and schedule related aspects, when choosing PDS for their projects. Though the case study of this research is based on the sample data obtained from the construction industry, the same methodology and statistical process can be applied to other industries and factors/variables of interest when the study sample data are unbalanced and the normality and homogeneity of variance assumptions are violated.