Enhancing the performance of exponentially weighted moving average charts: discussion

Abbas et al. (Abbas N, Riaz M, Does RJMM. Enhancing the performance of EWMA charts. Quality and Reliability Engineering International 2011; 27(6):821-833) proposed the use of signaling schemes with exponentially weighted moving average charts (named as 2/2 and modified − 2/3 schemes) for their improved design structures. A two-sided control structure of these schemes is given in the paper. The computational results in some of the tables of that paper for modified − 2/3  are mistakenly given for the one-sided control structure. The corrected two-sided results are provided here. It is noticed that the superiority of the proposed scheme over the classical exponentially weighted moving average chart remains but is less pronounced.