Max-EWMA chart was developed and evaluated by Almulhim et al. (2024) in terms of the average run length (ARL) and standard deviation (SD) of the run length distribution. To the best of our knowledge, Almulhim et al. (2024) overestimated the performance of the chart by reporting very small out-of-control average run lengths (ARL₁) which makes the chart unnecessarily too good.  Again, the discussion of the results in the work is not detailed which limits better understanding of the chart’s monitoring behavior. This study re-evaluates the Max-EWMA chart performance for joint monitoring of the parameters of lognormal processes with a detailed discussion to reflect the 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.

Keywords: Max-EWMA chart, Joint monitoring, Simulation, Average run length, Chart performance, Standard deviation of the run length