Margarethe Coelho, Subhabrata Chakraborti, Marien Alet Graham


A carefully done Phase I analysis is a vital part of an overall statistical process control and monitoring regime. Distribution-free control charts can play a useful role in this analysis, as a parametric model assumption often cannot be adequately verified. The performance of two distribution-free charts for the location – the mean-rank and the median chart – are compared in this paper. For benchmarking reasons, the parametric -chart is included in the comparisons. It is seen that the distribution-free charts are in-control robust, whereas the -chart is not, and they both perform similarly to the -chart for normally distributed data. However, for non-normal data, they both outperform the -chart. The results provide evidence in favour of using distribution-free Phase I charts in practice. Concluding remarks and suggestions for future research are given.


Retrospective phase; nonparametric; simulation

Full Text:


DOI: https://doi.org/10.7166/26-2-1026


  • There are currently no refbacks.

Copyright (c) 2015 The South African Journal of Industrial Engineering

ISSN 2224-7890 (on-line)

Powered by OJS and hosted by Stellenbosch University Library and Information Service since 2011.


This journal is hosted by the SU LIS on request of the journal owner/editor. The SU LIS takes no responsibility for the content published within this journal, and disclaim all liability arising out of the use of or inability to use the information contained herein. We assume no responsibility, and shall not be liable for any breaches of agreement with other publishers/hosts.

SUNJournals Help