Joint X̄ and R Charts with Variable Sample Sizes and Sampling Intervals

Abstract

Recent studies have shown that the X̄ chart with variable sampling intervals (VSI) and/or with variable sample sizes (VSS) detects process shifts faster than the traditional X̄ chart. This article extends these studies for processes that are monitored by both the X̄ and R charts. A Markov chain model is used to determine the properties of the joint X̄ and R charts with variable sample sizes and sampling intervals (VSSI). The VSSI scheme improves the joint X̄ and R control chart performance in terms of the speed with which shifts in the process mean and/or variance are detected.

• Adjusted Average Time to Signal
• Markov Chains
• Statistical Process Control
• Variable Sample Size
• Variable Sampling Intervals

Additional information

Notes on contributors

Antonio F. B. Costa

Dr. Costa is an Assistant Professor in the Department of Production. He is a Member of ASQ. His email address is [email protected].