Research Summary

My research focuses on service operations management, which covers a wide range of industries including hospitals, ride-hailing platforms, amusement parks, and supermarkets. Because customers in these environments typically wait for service, queueing systems are useful for the management of service systems. I am especially interested in managing queueing systems from both mathematical and behavioral perspectives.

To bridge these two perspectives, I employ a blend of methodologies that moves from the theoretical analysis of stochastic process models to the analysis of data from behavioral lab experiments and the field. By combining these analytical and numerical tools, my goal is to develop rigorous yet practically useful models and solutions that improve how service systems work for everyone.

Journal Publications

Predicting Left-Without-Being-Seen in an Emergency Department as a Dynamic Risk Ravid, Y., R. Ibrahim, J. Hu, K. Pasupathy, D. Nestler, V. Sarhangian, and P. Afeche.
American Journal of Emergency Medicine, forthcoming.
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Shortest-Job-First Scheduling in Many-Server Queues with Impatient Customers and Noisy Service-Time Estimates Dong, J. and R. Ibrahim.
Operations Research, forthcoming.
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On Customer (Dis)honesty in Priority Queues: The Role of Lying Aversion Rodriguez, A. E., Ibrahim, R. and D. Zhan.
Management Science, 71(1), 2025, pp. 844-860. Second place in Behavioral OM best working paper (2021) | Finalist in IBM best student paper (A. Estrada) (2021)
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The Effect of Removing the Four-Hour Access Standard in the ED: A Retrospective Observational Study Momesso, T., B. Gokpinar, R. Ibrahim, and A. Boyle.
Emergency Medicine Journal, 40, 2023, pp. 630-635.
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Personalized Scheduling in Service Systems Ibrahim, R.
Queueing Systems: 100 Views on Queueing (SI), 100, 2022, pp. 445-447.
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On the SRPT Scheduling Discipline in Many-Server Queues with Impatient Customers Dong, J. and R. Ibrahim.
Management Science, 67(12), 2021, pp. 7291-7950.
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Eliciting Human Judgment for Prediction Algorithms Ibrahim, R., Kim, S-H., and J. Tong.
Management Science, 67 (4), 2021, pp. 1993-2656.
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A General Framework to Compare Announcement Accuracy: Static vs LES-based Announcement Bassamboo, A. and R. Ibrahim.
Management Science, 67 (7), 2021, pp. 3985-4642.
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Flexible Workers or Full-Time Employees? On Staffing Service Systems with a Blended Workforce Dong, J. and R. Ibrahim.
Operations Research, 68(4), 2020, pp. 965-1284.
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Predicting Surgery Duration: Physician Input, Statistical Models, and Combined Models Ibrahim, R. and S-H Kim.
Seoul Journal of Business, 25(2), 2019, pp. 1-33.
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Sharing Delay Information in Service Systems: A Literature Survey Ibrahim, R.
Queueing Systems, 89(1-2), 2018, pp. 49-79.
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Managing Queueing Systems Where Capacity Is Random and Customers Are Impatient Ibrahim, R.
Production and Operations Management, 27(2), 2018, pp. 207-383. Finalist in INFORMS JFIG paper competition (2015)
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Does the Past Predict the Future? The Case of Delay Announcements in Service Systems Ibrahim, R., Armony, M., and A. Bassamboo.
Management Science, 63(6), 2017, pp. 1762-1780.
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Modeling and Forecasting Call Center Arrivals: A Literature Survey and a Case Study Ibrahim, R., Ye, H., L'Ecuyer, P. and H. Shen.
The International Journal of Forecasting, 32(3), 2016, pp. 865-874.
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Designing Individualized Treatment: An Application to Anticoagulation Therapy Ibrahim, R., Kucukyazici, B., Verter, V., Gendreau, M. and M. Bolstein.
Production and Operations Management, 25 (5), 2016, pp. 902-918.
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Inter-Dependent, Heterogeneous, and Time-Varying Service-Time Distributions in Call Centers Ibrahim, R., L'Ecuyer, P., Shen, H., and M. Thiongane.
The European Journal of Operational Research, 250, 2016, pp. 480-492.
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Forecasting Call Center Arrivals: Fixed-Effects, Mixed-Effects, and Bivariate Models Ibrahim, R. and P. L'Ecuyer.
Manufacturing and Service Operations Management, 15(1), 2013, pp. 72-85.
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Wait-Time Predictors for Customer Service Systems with Time-Varying Demand and Capacity Ibrahim, R. and W. Whitt.
Operations Research, 59(5), 2011, pp. 1106-1118.
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Real-Time Delay Estimation Based on Delay History in Many-Server Service Systems with Time-Varying Arrivals Ibrahim, R. and W. Whitt.
Production and Operations Management, 20(5), 2011, pp. 654-667.
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Real-Time Delay Estimation in Overloaded Multiserver Queues with Abandonment Ibrahim, R. and W. Whitt.
Management Science, 55(10), 2009, pp.1729-1724.
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Real-Time Delay Estimation Based on Delay History Ibrahim, R. and W. Whitt.
Manufacturing and Service Operations Management, 11(3), 2009, pp 397-415.
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Referee Proceedings and Book Chapters

On Queues with a Random Capacity: Some Theory, and an Application Ibrahim, R.
In: Hu M. (eds) Sharing Economy, Springer Series in Supply Chain Management, 6, 2019, pp. 279-316.
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On the Modeling and Forecasting of Call Center Arrivals Ibrahim, R., L'Ecuyer, P., Regnard, N., and H. Shen.
Proceedings of the 2012 Winter Simulation Conference, pp. 23-35.
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Delay Predictors for Customer Service Systems with Time-Varying Parameters Ibrahim, R. and W. Whitt.
Proceedings of the 2010 Winter Simulation Conference, pp. 2375-2386.
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Real-Time Delay Estimation in Call Centers Ibrahim, R. and W. Whitt.
Proceedings of the 2008 Winter Simulation Conference, pp. 2876-2883.
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Completed Drafts

Fair and Efficient Scheduling with Stratified No-Show Prediction Liu, A., Dong, J. and R. Ibrahim.
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Credibility and Effectiveness of Information Design in Service Operations Rodriguez, A. E., Ibrahim, R. and M. Kremer.
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Designing Doctor-Patient Shared Decision-Making Processes under Bounded Rationality Tuncalp, F., Ibrahim, R., Kim, S-H., and J. Tong.
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The Effects of Information Granularity on Abandonment and Congestion in Non-Stationary Priority Queues Afeche, P., Hu, J., Ibrahim, R. and V. Sarhangian.
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Doctoral Thesis

Real-time delay prediction in customer service systems
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