A note on “designing of a hybrid exponentially weighted moving average”
Many procedures have been introduced to improve the efficacy and performance of the exponentially weighted moving average (EWMA) control chart. The objective of these research studies is to introduce an efficient and precise monitoring method to detect smaller shifts in the process mean. Azam et al.  presented a new control chart called hybrid exponentially weighted moving average (HEWMA); where they have developed a new model and derived new control schemes. However, minor mistakes were observed in the article. This note will modify Azam et al.’s article in order to get the maximum benefit out of their proposed new model.
KeywordsAverage run length (ARL) Average sample size (ASS) Exponentially weighted moving average (EWMA) Hybrid exponentially weighted moving average (HEMWA) Control chart
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The authors appreciate the work done by Muhammad Azam, Muhammad Aslam, and Chi-Hyuck Jun and their effort to improve the EWMA chart. They have indeed introduced a new EWMA control scheme which is very effective and sensitive in detecting small shifts in the industrial processes. Of course, any such effort may have minor typos and can be corrected easily.