Risk Modeling of Dependence among Project Task Durations

Project risk management requires assessments of project duration and activity criticality. However, the assessments can be strongly influenced by dependence between task durations. In light of the need to address the dependence, this work proposes a computer simulation model to incorporate and augment NORTA, a method for multivariate random number generation. The model allows arbitrarily specified marginal distributions for task durations (need not be members of the same distribution family) and any desired correlation structure. This level of flexibility is of great practical value when systematic data is unavailable and planners must rely on experts' subjective estimation. Application of the model is demonstrated through scheduling a road pavement project. Model validation is done by showing that sample correlation coefficients between task durations closely match the originally specified ones. Empirical comparisons between the proposed model and 2 conventional approaches, PERT and conventional simulation (without correlations), are used to illustrate the model's usefulness.

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