Schedule management is a particularly important activity for companies that manage their business with an engineer-to-order approach. In many cases, especially in smaller enterprises, projects duration, estimated applying deterministic approaches or even referring to own experiences, are significantly inaccurate or overestimated. For these reasons, in this paper which is the extended version of a previous work presented at the Summer School “F. Turco”, authors propose an application of a probabilistic simplified approach on a case study comparing the results to those deriving from deterministic approaches and actual durations. Methodologies have been applied according to the sequence defined by Project Management Institute. To estimate activities durations both physical and statistical models have been used, instead entire projects duration has been calculated through critical path method. Results comparison shows that adopting a statistical approach leads to tolerable complications but allows to get more accurate estimations. Moreover, the possibility to consider most probable, optimistic and pessimistic duration allows enterprise to take into account potential risks that could delay project conclusion. This application is focused on a particular case study nevertheless conclusion could be common to many other organizations.