A probabilistic approach to determining the length of schedule works

Summary. Research is devoted to scheduling and solving scientific problem of improving the reliability of the planning and schedule implementation. This article discusses the factors that affect the estimated time of performing any construction and assembly operations in the schedule. The method is based on the approach that the time of completion of a scope of work is derived from the performance of a performer and the intensity of the work. To use this approach it is required to apply statistical data of kib performer at similar facilities in the past. So work completion time is not determined value but range (interval) of possible values that can be described by a normal distribution, β- and α-distributions. According this method any planned work in the schedule is shown as "fan" function, which allows to see an increase of uncertainty over time. The thesis describes a method of calculation of the work organization taking into account such uncertainty. We describe the most typical cases of interlinkages between works in the calendar plan, performed by the proposed method. The proposed approach allows to neutralize the contradiction between the probabilistic nature of real processes and deterministic methods of their description. The presence of the of the determined value of a parameter only is not enough, because it is uncertain its position in the possible range of values from the minimum to the maximum. Manufacturing processes and conditions defining the performance indicators are in the future, and prediction (forecasting) of their values can be done only with a certain level of probability. Therefore, schedules based on real, probabilistic nature of their performance, allows you to get even more pessimistic values, but at the same time more reliable probability of achievement.