ABSTRACT
This article presents a method for scheduling a project affected by risk. The times required to carry out tasks are modelled using type-2 fuzzy numbers. The parameters of these type-2 fuzzy numbers are given by experts: the lower membership function corresponding to the duration of a task in stable conditions, with no risks materialising, and the upper membership function corresponding to the duration of a task in the case when risks occur. The proposal was applied to a real world construction project. Using type-2 fuzzy numbers enabled to create a schedule in which time buffers modelling a potential extension of execution time in the situation of risks materialisation were used. Finally, a case study for operating theatre in hospital in Poland is presented. Here in scheduling the operation process both traditional type-1 and type-2 fuzzy numbers are used. Type-1 fuzzy numbers are used to model the duration of procedural activities and type-2 fuzzy numbers are used to model possible delays in the starting times of these activities. The time analysis of the operation process that was carried out resulted in the implementation of organisational changes which led to the decrease in to the decrease in the number of surgeries not performed by 16 per cent.
