Lower Confidence Bound for Process-Yield Index S _pk with Autocorrelated Process Data

Abstract

In this paper, the lower confidence bound for the process-yield index S _pk is developed for autocorrelated process data. A simulation study is conducted to assess the performance of the proposed index and two existing indices C _p and C _pk for various combinations of sample size, autoregressive parameter, and true index value. The simulation results confirm that the estimated S _pk performs better than the other two indices C _p and C _pk regarding bias and standard deviation. Additionally, the coverage rates of S _pk in most cases are greater than a 95% lower limit of the stated nominal. Two real examples are used to demonstrate the application of the proposed approach.

Key Words:

• Autocorrelated process
• lower confidence bound
• process-yield index.

Additional information

Notes on contributors

Fu-Kwun Wang

Fu-Kwun Wang is a Distinguished Professor in the Department of Industrial Management at the National Taiwan University of Science and Technology, Taiwan. His primary research interests are in reliability, quality and production management.

Yeneneh Tamirat

Yeneneh Tamirat is a Ph.D. candidate in the Department of Industrial Management at the National Taiwan University of Science and Technology, Taiwan. His research areas are statistical quality control and process capability analysis.