Analysis Process Dispersion Variation Tracked using a Mixed MA-EWMA Control Chart

Abstract

This study aims to develop a combined Moving Average - Exponentially Weighted Moving Average Control Chart with standard deviation based (MA-EWMAS chart) that can be used to identify changes in standard deviation in processes under a normal distribution. The average run length (ARL), standard deviation of run length (SRL), and median run length (MRL) are used to compare the performance of the proposed control chart with S, MAS, and EWMAS control charts. This benchmark is assessed using Monte Carlo (MC) simulations. Furthermore, actual data is used to apply the suggested control charts. For all levels of variation, the recommended control chart outperforms S, MAS, and EWMAS control charts in terms of detection performance, as indicated by the performance comparison results. Additionally, the MA-EWMAS chart demonstrates superior performance in managing process variability for moderate and large subgroup sizes across all magnitudes of shift parameters. One way to assess the control chart's effectiveness is to apply the suggested chart to track the fruit juice and wafer coating production process and verify that it complies with standards. The results of the simulations were found to align with the actual data.