On the improvement of one-sided S control charts
The most common charting procedure used for monitoring the variance of the distribution of a quality characteristic is the S control chart. As a Shewhart-type control chart, it is relatively insensitive in the quick detection of small and moderate shifts in process variance.
The performance of the S chart can be improved by supplementing it with runs rules or by varying the sample size and the sampling interval. In this work, we introduce and study one-sided adaptive S control charts, supplemented or not with one powerful runs rule, for detecting
increases or decreases in process variation. The properties of the proposed control schemes are obtained by using a Markov chain approach. Furthermore, a practical guidance for the choice of the most suitable control scheme is also provided.
Keywords: Shewhart control charts; adaptive control charts; adjusted average time to signal; process variation; runs rules; sample standard deviation
Document Type: Research Article
Affiliations: 1: Department of Statistics and Actuarial-Financial Mathematics,University of Aegean, Greece 2: Department of Statistics and Insurance Science,University of Piraeus, Greece
Publication date: 01 December 2011
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