Two Scheduling Models, One Project: Are Models Applicable in Case of Real Projects?

Modern project management has developed numerous techniques based on mathematical models in order to be able to plan the projects’ processes in time, their costs and resources. Even though a significant majority of the users do not know that, there are hypotheses behind every technique. These hypotheses help simplify the problems to such an extent that they can be handled by mathematical tools. In this paper, two mathematical models are examined, compared; then the results are analyzed. The first model is the cost optimization model, which can be applied to determine the optimal direct cost corresponding to a given project duration. With the help of the other model the expected distribution of the project duration is determined, assuming that the distribution of the activity durations is stochastic. Both models are adapted in Precedence Diagramming networks, consequently, PDM/cost and PDM/PERT expressions are used in the paper. A PDM network plan made by the contractor of a construction project is developed further into a PDM/cost and a PDM/PERT model in a case study described in the paper. Then calculations are performed according to the models. Finally, consequences are drawn, and attempts are made to find common points of interpretation of the two models.