Auxiliary information based maximum EWMA and DEWMA charts with variable sampling intervals for process mean and variance

Monitoring Coefficient of Variation Using Variable Sampling Interval Double Exponentially Weighted Moving Average Charts

“…In Equations ( 10) and (11), W is the coefficient of UWL of the corresponding VSI DEWMA-2 γ charts. In the previous related research(see Haq and Akhtar [18] ), a common choice is to take 0.1  can be adopted according to the specific needs of the practitioners. For simplicity, we only consider the case ( ) ( ) 0.1,1.9 , sl hh = and 12 0.5  == .…”

“…Castagliola, Celano, Fichera et al [17] developed a VSS EWMA chart to monitor the sample variance and it was shown the chart outperforms the Fixed Sample Size and Interval (FSSI) chart. More examples of researches on VSI or VSS charts include Haq and Akhtar [18], Reynolds, Amin and Arnold [19] and Reynolds and Arnold [20], among others. In addition, some researchers applied the VSS or VSI features to enhance the performance of the traditional CV charts (see, Castagliola, Achouri, Taleb et al [21], Khaw, Khoo, Yeong et al [22], Muhammad, Yeong, Chong et al [23], Nguyen, Nguyen, Tran et al [24], Yeong et al [1], Tran and Heuchenne [25]).…”