On Designing a Moving Average-Range Control Chart for Enhancing a Process Variation Detection

This research purpose is to create a moving average control chart for detecting a change in process variations with a range so-called MA-R chart and to compare the performance of the MA-R chart with the R, S, and MA-S control charts for detecting variation changes. The purposed control chart is an effective alternative to the R control chart using the moving average based on the sample range. The coefficients for the control limit of MA-R varying the sample sizes (m) and the width for moving average calculation (w) are presented. Comparison and application to real data show that the MA-R control chart is more effective at detecting variations at all levels than the R and S control charts. Furthermore, when the magnitude of the variation is small, the MA-R chart becomes more effective as w increases.