Economic statistical design for and S² control charts: A markov chain approach

Abstract

Over-adjustment to a process may result in shifts in process mean, process variance, or both, ultimately affecting the quality of products. A statistically constrained model is developed for the joint economic statistical design of and S² control charts to control both process mean and variance. The objective is to determine the design parameters of the control charts, which minimize the total quality control cost. A Markov chain approach is used to derive the model. Application of the model is demonstrated through a numerical example.

Keywords:

• Control charts
• Special causes
• Adjustment
• Markov chain
• Renewal reward processes