Horizontal cumulative variance chart: A quality control scheme monitoring shifts in process variation

In this study, we consider a new quality control scheme named horizontal cumulative variance (HCUV) which is designed to monitor the shifts in process variation. We start our discussions with the statistical properties of the distribution of cumulative squares then further to that of cumulative variances, and the mathematical measures to have a horizontal shape of these control schemes. We then propose HCUV. To illustrate the charts, we first run HCUS and HCUV with simulated data. We finally apply HCUV to chemical process data obtained from a real chemical manufacturing company. The illustration suggests that the HCUV scheme have the potential for practically monitoring changes in process variation. Copyright © 2017 Inderscience Enterprises Ltd.