Date of Original Version
The authors discuss the methodologies for constructing quality control charts by cumulative square and cumulative variance methodologies. These methodologies correspond to the EWMS and EWMV methods proposed by MacGregor and Harris (1993). Based on the distributions of the quality control chart statistics, we focus on the average (mean) cumulative square and average (mean) cumulative variance schemes to arrive at control limits appearing as parallel lines seen in stand Shewhart control charts. Last , we utilize the Box quadratic form and approximation to deal with the complexities of cumulative variance where means vary over time.
Pan, X., & Jarrett, J. E. (2013). Constructing SPC Charts by Cumulative Square and Cumulative Variance Methodologies. International Journal of Economics and Management Engineering, 3(6), 247-253.