Estimating the mean completion time of PERT networks with exponentially distributed durations of activities

In order to compute the exact values of the characteristics for PERT networks with exponentially distributed durations of activities, one needs to explore the state space of a Markov chain. This method suffers from exponential state explosion. An approximate method for estimating the mean completion time of the above networks is proposed in this paper. The present method is of polynomial computational complexity. The accuracy of the method is compared with the best upper bound for the considered kind of networks.