Authors

• Marzieh Arbabi
• Zahra Rezaei Ghahroodi

Abstract

The principal function of a control chart is to help management distinguish different sources of variation in a process. Control charts are widely used as a graphical tool to monitor a process in order to improve the quality of the product. Chen and Hsieh (2007) have designed a T2 control chart using a Variable Sampling Size and Control limits (V SSC) scheme. They have shown that using the V SSC scheme results in charts with more statistical power to detect small to moderate shifts in the process mean vector than the other T2 charts. In this paper, we develop an economic design for the T2 −V SSC chart to help determine the design parameters and then minimize the cost model proposed by Costa and Rahim (2001) using a Genetic Algorithm (GA) approach. We also compare economic design of the T2 −V SSC chart with the T2 −DWL, T2 −V SSI and T2 −FRS charts so as to choose the best option and, finally, carry out a sensitivity analysis to investigate the effects of model parameters on the solution of the economic design.

Keywords

• Adjusted average time to signal (AATS)
• economic design (ED)
• Genetic algorithm (GA)
• Markov Chain
• multivariate control charts
• Sensitivity analysis
• variable sample size and control limits (V SSC)