Adaptive Control Limits for Bivariate Process Monitoring (1996)
P. Grabov, QA&R, ALD Ltd., Israel
D. Ingman, QA&R, Technion, Haifa, Israel

Variables control charts implement process state testing by separately assessing the measures of central tendency and spread.
This work, based on the ideas of bivariate process control, analyzes whether the standard charting method could be considered as optimal and present an alternative mode of process evaluation-biparameter description in terms of the joint distribution of sample averages and standard deviations.