ISO 28593:2017 属性による受け入れサンプリング手順—発信品質を制御するためのクレジット原則に基づく受け入れゼロサンプリングシステム | ページ 2

Foreword

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This document was prepared by Technical Committee ISO/TC 69, Applications of statistical methods, Subcommittee SC 5, Acceptance sampling.

This first edition of ISO 28593 cancels and replaces ISO 18414:2006, of which it constitutes a minor revision to change the reference number from 18414 to 28593.

With the view to achieve a more consistent portfolio, TC 69/SC 5 has simultaneously renumbered the following standards, by means of minor revisions:

Cross references between the above listed documents have been corrected in the minor revisions.

A list of all documents in the new ISO 28590 - ISO 28599 series of International Standards can be found on the ISO website.

1 Scope

1.1 This International Standard specifies a system of single sampling schemes for lot-by-lot inspection by attributes. All the sampling plans of the present system are of accept-zero form, i.e. no lot is accepted if the sample from it contains one or more nonconforming items. The schemes depend on a suitably-defined average outgoing quality limit (AOQL), the value of which is chosen by the user; no restrictions are placed on the choice of the value of the AOQL or on 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 AOQL in the long run.

1.2 The schemes are intended to induce a supplier, through the economic and psychological pressure of lot non-acceptance and consequent loss of accumulated credit, 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 AOQL. This objective is achieved by a progressive reduction in the sample size in response to good quality history.

1.3 The schemes are designed to be applied to a series of lots from each supplier. The credit principle provides:

• a) automatic protection to the customer if a deterioration in quality is detected, by means of a total loss of accumulated credit and reversion to a relatively large sample size whenever a nonconforming item is found, and 100 % inspection of
  • 1) the first lot if it is not accepted, or
  • 2) any non-accepted lot that immediately follows a non-accepted lot;

• b) an incentive to reduce sampling costs (by means of a progressive reduction in required sample size) if consistently good quality is achieved.

1.4 This International Standard is designed for use under the following conditions:

• a) where the inspection procedure is to be applied to a series of lots of discrete items that are intended to be identical, and which are all supplied by one producer using one production process (If there are different producers or production processes, this International Standard is intended to be applied to each one separately.);
• b) where one or more quality characteristics of these products are taken into consideration, which must all be classifiable as either conforming or nonconforming;
• c) where the inspection error involved in classifying the state of a product's quality characteristic(s) is negligible;
• d) where inspection is non-destructive.

This International 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 with certainty, regardless of how long or short individual suppliers' series may be. This International 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.

2 Normative references

The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 3534-2 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

Bibliography