A critique of a variety of "memory-based" process monitoring methods. Issue 1 (1st January 2023)

• Record Type: Journal Article
• Authors: Knoth, Sven; Saleh, Nesma A.; Mahmoud, Mahmoud A.; Woodall, William H.; Tercero-Gómez, Víctor G.
• Is Part Of: Journal of quality technology. Volume 55:Issue 1(2023)
• Page Start: 18
• Page End: 42
• Publication Date: 2023-01-01
• Subjects: Control chart -- cumulative sum (CUSUM) chart -- exponentially weighted moving average (EWMA) chart -- mixed control charts -- statistical process monitoring; Quality control -- Periodicals; Qualité -- Contrôle -- Périodiques; Quality control; Quality control; Periodicals; 620.0045
• DOI: 10.1080/00224065.2022.2034487
• Languages: English
• ISSNs: 0022-4065

Abstract

Abstract: Many extensions and modifications have been made to standard process monitoring methods such as the exponentially weighted moving average (EWMA) chart and the cumulative sum (CUSUM) chart. In addition, new schemes have been proposed based on alternative weighting of past data, usually to put greater emphasis on past data and less weight on current and recent data. In other cases, the output of one process monitoring method, such as the EWMA statistic, is used as the input to another method, such as the CUSUM chart. Often the recursive formula for a control chart statistic is itself used recursively to form a new control chart statistic. We find the use of these ad hoc methods to be unjustified. Statistical performance comparisons justifying the use of these methods have been either flawed by focusing only on zero-state run length metrics or by making comparisons to an unnecessarily weak competitor.