Real data analysis and simulation results show that call centers have the fea- tures of redial (re-attempt after an abandonment) and reconnect (re-attempt after an answered call), and ignoring them would lead to inaccurate estima- tion of the total inbound volume. Thus, we propose a queueing model that includes both features. In such a model, the total volume consists of the fresh calls (initial call attempts), the redials and reconnects. In practice, the total volume is used to make forecasts, while according to the simulation re- sults, this could lead to high forecast errors, and subsequently wrong stang decisions. However, most of the call center data sets do not have customer- identity information, which makes it dicult to identify how many calls are fresh and what fractions of the calls are redials and reconnects. Motivated by this, we propose an estimation model to estimate the num- ber of fresh calls, and the redial and reconnect probabilities, using real call center data that has no customer-identity information. We show that these three variables cannot be estimated simultaneously. However, it is empir- ically shown that if one variable is given, the other two variables can be estimated accurately with relatively small bias. We show that our estima- tions of redial and reconnect probabilities and the number of fresh calls are close to the real ones, both via real data and simulation.
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European Journal of Operational Research

van der Mei, R. (2015). On the Estimation of the True Demand in Call Centers
with Redials and Reconnects. European Journal of Operational Research.