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Monitoring process variability using auxiliary information

2007; Springer Science+Business Media; Volume: 23; Issue: 2 Linguagem: Inglês

10.1007/s00180-007-0084-6

1613-9658

Muhammad Riaz,

Advanced Statistical Methods and Models

In this study a Shewhart type control chart namely V r chart is proposed for improved monitoring of process variability (targeting large shifts) of a quality characteristic of interest Y. The proposed control chart is based on regression type estimator of variance using a single auxiliary variable X. It is assumed that (Y, X) follow a bivariate normal distribution. The design structure of V r chart is developed and its comparison is made with the well-known Shewhart control chart namely S 2 chart used for the same purpose. Using power curves as a performance measure it is observed that V r chart outperforms the S 2 chart for detecting moderate to large shifts, which is main target of Shewhart type control charts, in process variability under certain conditions on ρ yx . These efficiency conditions on ρ yx are also obtained for V r chart in this study.