A Comparative Study of Exponential Time between Events Charts

Abstract

Control charts based on time between events (TBE) data have been shown to be useful for monitoring production or failure processes where defect or failure occurrence can be recorded over time. One type of TBE chart is set up with probability control limits, e.g. the Cumulative Quantity Control (CQC) chart and its extension CQC-r chart, which monitors the quantity inspected until the occurrence of a fixed number of defects (r). Another type of TBE chart studied in the literature is to apply the CUSUM and EWMA methods to TBE data directly. In this paper, some exponential TBE charts are compared based on their Average Time to Signal (ATS) performance. Different in-control ATS values are used in order to evaluate its effect on the performance of the TBE charts. Based on the comparison analysis, some recommendations are made as guidelines for employing a proper chart under different situations.

Key Words:

• CQC-r chart
• cumulative quantity control (CQC) chart
• exponential CUSUM
• exponential EWMA
• time between events (TBE) charts

Additional information

Notes on contributors

J. Y. Liu

Jiying Liu is a research scholar in the Department of Industrial and Systems Engineering, National University of Singapore. She received her ME in Industrial Engineering from the Northwestern Polytechnic University at Xi’an, China. Her research interest is statistical quality control.

M. Xie

Min Xie is a Professor of Industrial and Systems Engineering, National University of Singapore. He received his PhD in Quality Technology from Linkoping University in 1987. His research area includes quality, reliability and applied statistics. Prof Xie is an author or co-author of over 100 journal papers and 6 books in this field. He serves as editor or associate editor of IJRQE, QTQM, IIE Transactions, IEEE Transactions on Reliability and several other journals. He is a Fellow of IEEE.

T. N. Goh

Thong Ngee Goh is a Professor of Industrial and Systems Engineering at the National University of Singapore. He obtained his PhD from the University of Wisconsin-Madison. Prof Goh has been internationally recognized for his expertise in quality engineering and management. He is an author of numerous papers and a few books. He is an elected Fellow of ASQ as well as Academician of IAQ.

P. R. Sharma

Priya Ranjan Sharma received his PhD degree from National University of Singapore. After graduation, he joined Standard Chartered Bank in Singapore. Currently he is an Assistant Vice President in Credit Risk Management at OCBC Bank, Singapore.