Because almost 60–80% of the total costs for operating a contact centre involve wage and benefit expenses for personnel, determining the optimal number of agents available is of great importance in call centre management. In modern call centres, working hours are divided into planning intervals with identical lengths. Each planning interval is typically assumed to be a homogeneous Poisson process in a steady state, and simple queuing models, such as Erlang-C (M/M/c), are often applied to determine the optimal staffing levels of the planning intervals. However, since the actual length of the planning interval in practice is relatively short, the basic assumption of staffing analysis could be violated. In this paper, we numerically analyze an M/M/c+M call centre’s behavior in a transient state. As a result, we can determine appropriate staffing levels of a call centre with short planning intervals which do not assume to be in a steady state.
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