A fuzzy set theoretic interpretation of economic control limits

Abstract It has been the practice in industry that product specification limits have been used to judge between ‘good’ and ‘bad’ product. It is generally assumed that a given unit of product either does or does not conform to specifications. Traditional acceptance control charts have contributed to this notion. The present paper suggests that situations exist where a concept of graded conformance might provide a more accurate representation of reality. It exploits the theory of fuzzy sets to demonstrate how acceptance control charts can be constructed to explicitly account for the degree of conformance exhibited by each unit or sample of product.