Title: A Johnson's type transformation EWMA-S² control chart

Authors: Philippe Castagliola, Giovanni Celano, Sergio Fichera

Addresses: Universitede Nantes & IRCCyN UMR CNRS 6597, 2 avenue du Professeur Jean Rouxel, BP 539 – 44475 Carquefou Cedex, France. ' Universita di Catania, Dipartimento di Ingegneria Industriale e Meccanica, Viale Andrea Doria, 6 95125 Catania, Italy. ' Universita di Catania, Dipartimento di Ingegneria Industriale e Meccanica, Viale Andrea Doria, 6 95125 Catania, Italy

Abstract: This article demonstrates how a four parameters (bounded) Johnson S_B transformation combined with an EWMA approach can be used to monitor the sample variance of a process. The resulting chart will be called an EWMA-J-S² chart. In this article, the computation of both the control limits and the parameters of the Johnson S_B transformation of the EWMA-J-S² chart are explained. An easy-to-use table providing useful constants and an illustrative example are given. The distributional properties of the transformed sample variance are derived and, finally, an optimal design strategy based on the ARL is presented and a list of optimal design parameters for the EWMA-J-S² chart is provided.

Keywords: sample variance; EWMA charts; Johnson S_B; distribution; process monitoring; control charts; staatistical process control; SPC; optimal design.

DOI: 10.1504/IJQET.2010.034611

International Journal of Quality Engineering and Technology, 2010 Vol.1 No.3, pp.253 - 275

Published online: 13 Aug 2010 *

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