Mohsen Varmazyar - Department of Industrial Engineering, Sharif University of Technology, Tehran, Iran
Raha Akhavan-Tabatabaei - School of Management, Sabanci University, Istanbul, Turkey
Nasser Salmasi - Department of Industrial Engineering, Sharif University of Technology, Tehran, Iran
Mohammad Modarres - Department of Industrial Engineering, Sharif University of Technology, Tehran, Iran

Based on the increasing need for hospital services to the people during the recent decades, the hospitals need to use their resources more efficiently. Operating Theatre Rooms (OTR) are one of the most cost-intensive and revenue-generating service sectors in hospitals [1]. Efficient scheduling of OTR activities is complicated by the variability inherent in surgical procedures. Thus, accurate time distributions modeling is critical in constructing an optimal planning and scheduling scheme, reducing delays for patients and care providers as well as reducing overtime and under-utilization of OTR. Currently, some hospitals use traditional methods and others use commercial software packages to schedule their OTRs, but both methods rely on historical surgery durations as input [2]. Therefore, offering a scientific method to estimate the duration of surgeries in the OTR could benefit the improvement of its scheduling and planning.