Cumulative Sum (CUSUM) and Exponentially Weighted Moving Average (EWMA) Control Charts Approaches in Monitoring Crime Rate

Abstract

This paper is aimed at monitoring crime rate using Cumulative Sum (CUSUM) and the Exponentially Weighted Moving Average (EWMA) control charts.The crime data analyzed using these charts were extracted from the record office of the Nigeria Police Zonal Head Quarter, Irrua, Edo state. On monitoring process shift in crime rate using CUSUM and EWMA control charts, control parameters were varied in order to assess their performances. For CUSUM control chart, the decision interval(h)was varied at 2.0, 3.0, 4.0 and 5.0 while the EWMA schemes smoothening constant (w)was varied at 0.1, 0.15, 0.2 and 0.25. The finding of the study shows that CUSUM scheme with decision interval h = 2.0 performed optimally by detecting a shift in the process mean in monitoring of crime rate, while EWMA chart scheme with w = 0.2 performed optimally for EWMA chart schemes. The CUSUM control chartwas also observed to detect a smaller shift in the process mean compared to EWMA chart. Therefore, when a smaller shift in the process mean is desired, the CUSUM control chart scheme should be adopted.