Open Access Open Access  Restricted Access Subscription Access

A Nonparametric Control Chart for Process Variability Based on Quantiles

Vilas Yashwant Pawar, Digambar Tukaram Shirke, Shashikant Kuber Khilare

Abstract



Most of the control charts are based on assumption of normality. Control charts for non-normal process distributions have also been reported in literature. In absence of any knowledge about the process distribution, nonparametric chart is a good alternative. In the recent past number of nonparametric control charts have been studied. In the present work we propose a control chart for monitoring process variability, which is based on in-control quantiles. The chart is motivated from a nonparametric control chart based on in-control quartiles due to Amin et al. (1995). The proposed chart has been studied for its performance for various process distributions to monitor change in variability and has been compared with the existing nonparametric and parametric charts. It has attractive out-of-control Average Run Length performance and is very simple to use. We illustrate the chart through an example and recommend use of this chart to monitor process variability. Generalization of the chart will also be discussed in view to further improve its detection ability.

Keywords


Nonparametric, control chart, quantiles, process variability and average run length.

Full Text:

PDF


Disclaimer/Regarding indexing issue:

We have provided the online access of all issues and papers to the indexing agencies (as given on journal web site). It’s depend on indexing agencies when, how and what manner they can index or not. Hence, we like to inform that on the basis of earlier indexing, we can’t predict the today or future indexing policy of third party (i.e. indexing agencies) as they have right to discontinue any journal at any time without prior information to the journal. So, please neither sends any question nor expects any answer from us on the behalf of third party i.e. indexing agencies.Hence, we will not issue any certificate or letter for indexing issue. Our role is just to provide the online access to them. So we do properly this and one can visit indexing agencies website to get the authentic information.