The idea of process monitoring emerged so as to preserve and improve the quality of a manufacturing process. In this regard , control charts are widely accepted tools in the manufacturing sector for monitoring the quality of a process. However, a specific distributional assumption for any process is restrictive and often criticized. Distribution-free control charts are efficient alternatives when information on the process distribution is partially or completely unavailable. In this article, we propose a distribution-free generally weighted moving average (GWMA) control chart based on the Wilcxon signed-rank statistic. Extensive simulation is performed to study the performance of the chart. The performance of the proposed chart is then compared with a number of existing the parametric GWMA chart for subgroup averages, a recently proposed GWMA chart on the sing statistic and an exponentially weighted moving average chart based on the signed-rank statistic.
The simulation results reveal that the proposed performs just as well as and in many cases better than the existing charts and therefore can serve as a useful alternative in practice. Copyright 2016 John Wiley & Sons, Ltd.