Monitoring Lognormal Parameters with Max-EWMA Chart: Revisitation of An Existing Work
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Keywords:
Lognormal Process; Max-EWMA Chart; Joint Monitoring; Simulation; Chart Performance; NormalityAbstract
Almulhim et al. (2024) proposed, developed, and evaluated a Max-EWMA chart on the metrics of average run length (ARL) and standard deviation (SD) of the run length distribution. The review of Almulhim et al. (2024), to the best of my knowledge, overestimated the performance of the chart. The overestimation is in terms of reporting smaller out-of-control average run lengths. than they should be, which makes the chart unnecessarily too good. Again, the results discussion in the work is not detailed, which limits better understanding of the chart’s monitoring behavior. This study re-evaluates the performance of the Max-EWMA chart for joint monitoring of lognormal parameters with a detailed discussion to reflect reality. The result confirms the overestimation of the performance of the Max-EWMA chart and provides improved insight into the sensitivity reality of the Max-EWMA chart.
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