Authors: Jean-Claude Malela-Majika; Eeva Maria Rapoo
Addresses: Department of Statistics, College of Science, Engineering and Technology, University of South Africa, UNISA 0003, Pretoria, South Africa ' Department of Statistics, College of Science, Engineering and Technology, University of South Africa, UNISA 0003, Pretoria, South Africa
Abstract: Control chart is one of the most important tools used in statistical process control and monitoring (SPCM) to detect changes in quality characteristics. This paper investigates the performance of the improved modified distribution-free synthetic and runs-rules charts combined with a Mann-Whitney (MW) chart, in terms of the average run length (ARL) and median run length (MRL) through intensive simulation. It is observed that the newly proposed improved modified synthetic and runs-rules MW charts present very attractive run-length properties and outperform the competing charts under non-normal underlying distributions. Numerical examples are given as illustration of the design and implementation of the proposed charts.
Keywords: nonparametric statistical process control; NSPC; MW statistic; conforming run-length chart; runs-rules; synthetic MW chart; Monte Carlo simulation.
International Journal of Quality Engineering and Technology, 2017 Vol.6 No.4, pp.219 - 248
Received: 18 Oct 2016
Accepted: 04 Aug 2017
Published online: 24 Aug 2018 *