Time series forecasting research has recently focused on developing
rather sophisticated methods for forecasting inbound call arrivals. However
there has been overwhelming evidence (Ibrahim& L'ecuyer, 2013;
Tandberg, Easom, & Qualls, 1995; Taylor, 2008a, 2010) that such
methods are outperformed by the simple Seasonal Moving Average
(SMA) method particularly at longer forecast horizons where capacity
planning decisions are made. Despite its attractiveness, the performance
of the SMA method has not been systematically evaluated, nor
have extensions been investigated. This study evaluates the
performance of the SMA method systematically varying the number of
seasonal periods included in the average to assess its impact on forecasting
accuracy across different data frequencies of 5 min, half-hourly
and hourly recorded call arrivals. The SMA method is compared to ‘simple’
and advanced benchmarks including seasonal ARIMA and the double
seasonal Holt-Winters exponential smoothing method of Taylor
(2003) forecasting 5 min to two weeks ahead.
A new hybrid forecasting method is proposed