A CUSUM chart using absolute sample values to monitor process mean and variance

In Statistical Process Control (SPC), when dealing with a quality characteristic x that is a variable, it is usually necessary to monitor both the mean value and variability. By inspecting the absolute value of sample mean shift, a single CUSUM chart (called the ABS CUSUM chart) has been devised by an optimization algorithm and fully investigated for this purpose. The optimization algorithm (called the holistic algorithm) facilitates the determination of the charting parameters of the charts and increases their overall detection effectiveness. The results of performance studies show that the overall performance of the ABS CUSUM chart is as good as an optimal 3-CUSUM scheme (a scheme incorporating three individual CUSUM charts). However, since the ABS CUSUM chart is easier for implementation and design, it may be more suitable for many SPC applications in which both mean and variance of a variable have to be monitored.