A variable sampling interval S2-EWMA control chart for monitoring the process variance. (27th December 2006)

• Record Type: Journal Article
• Authors: Castagliola, P.; Celano, G.; Fichera, S.; Giuffrida, F.
• Is Part Of: International journal of technology management. Volume 37:Number 1/2((2007)
• Page Start: 125
• Page End: 146
• Publication Date: 2006-12-27
• Subjects: sample variance -- exponentially weighted moving average -- EWMA control charts -- logarithmic transformation -- adaptive sampling interval -- variable sampling interval -- process monitoring -- SPC -- statistical process control -- quality control -- optimal design; Technology -- Management -- Periodicals; 658.4062
• Languages: English
• ISSNs: 0267-5730

Abstract

This paper proposes a Variable Sampling Interval version of the Fixed Sampling Interval S 2 -EWMA control chart developed by Castagliola (2004) and dedicated to the monitoring of the sample variance of a process. In this paper, we explain how the various parameters of this VSI S 2 -EWMA control chart can be computed and how the use of the VSI feature significantly improves the statistical efficiency of FSI S 2 -EWMA chart, thus representing an effective tool in the detection of process out-of-control conditions. An optimal design strategy based on the Average Time to Signal (ATS) is presented and a comparison with the FSI procedure is performed.