DIN ISO 18414:2012-02

This standard specifies a system of accept-zero single sampling schemes for lot-by-lot inspection by attributes. No restrictions are placed with respect to the choice of a suitable value of the average outgoing quality limit (AOQL) by the user or the sizes of successive lots in the series. The methodology ensures that the overall average quality reaching the customer or market-place will not exceed the average outgoing quality limit in the long run. The schemes are designed to be applied to a series of lots from each supplier. By a progressive reduction in the sample size in response to good quality history, the schemes are intended to induce a supplier to attempt to maintain a nonconformity-free process, while assuring, by means of the lowest practicable sample sizes, that the long-term percentage of nonconforming items delivered to the customer or market-place does not exceed the average outgoing quality limit. This standard is designed for use where the inspection procedure is to be applied to a series of lots of discrete items that are assumed to be identical, and which are all supplied by one producer using one production process. Further conditions for use are the taking into consideration of one or more quality characteristics of these products, which shall all be classifiable as either conforming or nonconforming, a negligible inspection error involved in assessing the state of a product's quality characteristic(s), a non-destructive test. This standard can be suitable for regulatory purposes, as control of the expected quality of items reaching the market-place is achieved with the smallest possible sample sizes, and long-term control of the realized, or actual quality level in the market-place is achieved, regardless of how long or short individual suppliers' series may be. This standard can be used by suppliers/producers, buyers/consumers and regulatory agencies to provide control of the expected quality of the totality of accepted product of each type from each source. The International Standard ISO 18414, which is the basis of this document, has been prepared in Technical Committee ISO/TC 69 "Applications of statistical methods", SC 5 "Acceptance sampling" (secretariat: BSI, United Kingdom). The committee responsible for the adoption into the national body of standards is NA 147-00-02 AA "Angewandte Statistik" ("Applied statistics") of Standards Committee NA 147 "Quality Management, Statistics and Certification" (NQSZ).