A new exponentially weighted moving average control chart for monitoring the coefficient of variation

The variable sampling interval run sumX‾control chart

“…Numerous works on control charts have been conducted over the years which have contributed to the area of SPC. Some of the recent ones were made by Ali and Riaz (2014), Teoh, Khoo, Castagliola, and Chakraborti (2014), Zhang, Li, Chen, and Wang (2014), Guo, Wang, and Cheng (2015), Nenes, Tasias, and Celano (2015) and Noorossana, Shekary, and Deheshvar (2015).…”

The efficiency of CUSUM schemes for monitoring the coefficient of variation

“… and Zhang et al . . The optimal couples ( K − ∗ , H − ∗ ) when τ = γ 1 / γ 0 = {0.5, 0.65, 0.8, 0.9} and ( K + ∗ , H + ∗ ) when τ = γ 1 / γ 0 = {1.1, 1.25, 1.5, 2} are presented in the Table , for n = {5, 7, 10, 15} and γ 0 = {0.05, 0.1, 0.15, 0.2}.…”

“…We compare proposed control charts to the EWMA‐ γ 2 control charts (denoted as ECV) introduced by Castagliola et al. and the modified EWMA‐ γ 2 control charts (denoted as MCV) introduced by Zhang et al . The out‐of‐control zero‐state A R L s of the CUSUM‐ γ 2 (left side), ECV (middle side), and MCV (right side) charts are presented in the Table .…”

“…, the literature has proposed several CV control charts. For further details, see, for instance, to name a few.…”

On the performance of coefficient of variation charts in the presence of measurement errors

“…In the SPC literature, Shewhart‐type control chart for monitoring the coefficient of variation (CV), which is defined as the ratio of the population standard deviation to the population mean, has already been investigated by Kang et al; subsequently, several control charts have been developed in the literature for monitoring the CV. For further details, see, for instance, Castagliola et al, Calzada and Scariano, Castagliola et al, Castagliola et al, Zhang et al, Castagliola et al, Castagliola et al, Amdouni et al, You et al, and Tran and Tran among others. For example, in textile manufacturing industry, the variation among tensile strength measurements from thin thread is significantly smaller than measurements taken from heavy thread because of the inherent physical properties of fiber.…”