A critique of a variety of “memory-based” process monitoring methods

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