A Study on Dummy Size to be Allocated to a Project Schedule

Abstract

The present study considers a new slack-based strategy for project scheduling, which introduces dummies. A dummy corresponds to an unforced slack time and is used for absorption of schedule delays caused by disturbances during the schedule execution. In this paper, we propose a mathematical model for determining an optimal dummy size K* to be inserted into a baseline schedule of a given project, considering the costs for dummies as well as those for schedule delays caused by disturbances. We first describe the concept of dummy and then formulate the total expected cost of a schedule with dummies. Clarified are the conditions on which a unique finite optimal dummy size K* exists, where the total expected cost is minimized. We also discuss the characteristics and the effectiveness of the proposed model through some numerical examples.