Improved Shewhart-Type Charts for Monitoring Times Between Events. Issue 3 (1st July 2017)

• Record Type: Journal Article
• Authors: Kumar, N.; Chakraborti, S.; Rakitzis, A. C.
• Is Part Of: Journal of quality technology. Volume 49:Issue 3(2017)
• Page Start: 278
• Page End: 296
• Publication Date: 2017-07-01
• Subjects: Average Run Length (ARL) -- ARL-Unbiased Control Chart -- Gamma Distribution -- High-Yield Processes -- Runs Rules -- Time Between Events -- tr -Chart; Quality control -- Periodicals; Qualité -- Contrôle -- Périodiques; Quality control; Quality control; Periodicals; 620.0045
• DOI: 10.1080/00224065.2017.11917995
• Languages: English
• ISSNs: 0022-4065

Abstract

Abstract : In high-yield processes with a low defect rate, the recommendation is to monitor the times between events (TBE) with variables control charts in order to overcome the weaknesses of conventional attribute control charts. In this paper, we incorporate supplementary runs rules into one of the existing Shewhart-type TBE charts, namely the tr -chart, in order to improve its small to moderate size-shift detection ability. Moreover, because the existing tr -chart based on probability limits is biased, we provide a procedure for designing a tr -chart, with or without runs rules, that is unbiased. The performance of several tr -charts with runs rules is investigated, whereas comparisons with EWMA and CUSUM charts are also given. It is seen that some of the runs rules enhanced tr -charts perform substantially better. A real-data example is provided for illustration and some concluding remarks are given.