A variable sampling interval sign chart for variability based on deciles

Abstract

In the present article, we develop a nonparametric quality control chart for monitoring process variability based on in-control deciles with variable sampling interval policy. The control chart based on in-control quartiles for monitoring process variability has been extended to the control chart based on in-control deciles following variable sampling interval policy. The performance of the proposed chart is studied for various process distributions. The proposed chart is simple to use and has an attractive out-of-control adjusted average time to signal performance. We illustrate an implementation of the chart through an example.

Keywords:

• Process control
• Adjusted average time to signal
• Sign test
• Nonparametric chart

Acknowledgments

Both the authors would like to acknowledge the financial support received from University Grants Commission under Major Research Project (F. No. 43-542/2014 (SR)) to carry out the research work.