Control charts based on medians

Abstract

Control charts are widely accepted and used in manufacturing industry. However, surprisingly often the data sets that they are used to analyse come from markedly non-normal populations. A modification of the control charts based on medians is proposed which overcomes non-normality problems. These median charts keep the traditional format and have reasonable power. The format is vital, for if the charts are to be used on the shop-floor then they must be acceptable and as we mimic accepted practice our proposals fulfil this requirement.