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Evaluation of mean and variance approximations in three point estimation of task completion times using the beta and the Kumaraswamy distribution

Published Online:pp 389-406

Estimation of task and project completion times within IT projects remains one of the most error-prone, but also most critical duties of an IT project manager. Various three-point methods of PERT have been evaluated by assuming that the true distribution is a beta-distribution. We evaluate PERT methods by comparing additionally with the Kumaraswamy distribution, which has an equal claim to be the true a-priori distribution for project completion times. We use skew and kurtosis in order to define test sets instead of simply choosing a range of shape parameters. We validate various approximations proposed in the literature and show that valid approximations are possible.


project management, expert judgement, mean and variance approximations, PERT, three-point estimations, task completion times, beta distribution, Kumaraswamy distribution