Design of multiple criteria sampling plans and charts

This paper develops formulas that can be used in the design of multiple criteria sampling plans or charts for fraction nonconforming, with sampling on variables or attributes. Products often have multiple requirements and the usual acceptance tests or charts do not take this into account, and hence the overall quality of the product may be in poor control. The authors design tests or charts on the basis of probability of Type I and Type II errors (α and β) that refer to acceptable and rejectable levels of the overall fraction of the product that is nonconforming. Further, recognizing that the average proportion of the product that is actually nonconforming on each of the characteristics may vary independently of the other characteristics, the present formulas give protection on a ‘worst case’ basis.