A Critical Review of Statistical Methods Used in Quality Control

Industrial quality control is one of the most important activities in modern production systems. Each undetected quality flaw may have disastrous consequence not only for the functioning of products, but also from the view point of safety and financial losses. The methods used in quality control remained in principle the same for many decades and the question therefore arises, whether they are still appropriate. The applied methods in quality control are mainly taken from statistics and are hardly questioned by quality control specialists since there is often no deep understanding of aims and properties of the applied methods particularly if they are formulated as ISO standards. As a consequence the results obtained may be misunderstood leading to wrong decisions. The aim of this paper is therefore to introduce statistical methods by outlining their essential properties and weaknesses.