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Inter-Dependent, Heterogeneous, and Time-Varying Service-Time Distributions in Call Centers

Ibrahim, R; L'Ecuyer, P; Shen, H; Thiongane, M; (2016) Inter-Dependent, Heterogeneous, and Time-Varying Service-Time Distributions in Call Centers. European Journal of Operational Research , 250 (2) pp. 480-492. 10.1016/j.ejor.2015.10.017. Green open access

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Abstract

Traditionally, both researchers and practitioners rely on standard Erlang queueing models to analyze call center operations. Going beyond such simple models has strong implications, as is evidenced by theoretical advances in the recent literature. However, there is very little empirical research to support that body of theoretical work. In this paper, we carry out a large-scale data-based investigation of service times in a call center with many heterogeneous agents and multiple call types. We observe that, for a given call type: (a) the service-time distribution depends strongly on the individual agent, (b) that it changes with time, and (c) that average service times are correlated across successive days or weeks. We develop stochastic models that account for these facts. We compare our models to simpler ones, commonly used in practice, and find that our proposed models have a better goodness-of-fit, both in-sample and out-of-sample. We also perform simulation experiments to show that the choice of model can have a significant impact on the estimates of common measures of quality of service in the call center.

Type: Article
Title: Inter-Dependent, Heterogeneous, and Time-Varying Service-Time Distributions in Call Centers
Open access status: An open access version is available from UCL Discovery
DOI: 10.1016/j.ejor.2015.10.017
Publisher version: http://dx.doi.org/10.1016/j.ejor.2015.10.017
Language: English
Additional information: © 2015 Elsevier B.V. After an initial embargo period, this manuscript is made available under a Creative Commons Attribution Non-commercial Non-derivative 4.0 International license (CC BY-NC-ND 4.0). This license allows you to share, copy, distribute and transmit the work for personal and non-commercial use providing author and publisher attribution is clearly stated. Further details about CC BY licenses are available at http://creativecommons.org/ licenses/by/4.0. Access may be initially restricted by the publisher.
Keywords: Applied probability; call centers; service times; agent heterogeneity; correlation
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > UCL School of Management
URI: http://discovery.ucl.ac.uk/id/eprint/1471894
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