A Generally Weighted Moving Average Signed-rank Control Chart

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 criticised. 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 Wilcoxon signed‐rank statistic. Extensive simulation is performed to study the performance of the proposed chart. The performance of the proposed chart is then compared with a number of existing control charts including the parametric GWMA chart for subgroup averages, a recently proposed GWMA chart based on the sign statistic and an exponentially weighted moving average chart based on the signed‐rank statistic. The simulation results reveal that the proposed chart performs just as well as and in many cases better than the existing charts and therefore can serve as a useful alternative in practice.