標準號：ISO 3951-5-2006
中文標準名稱：計量檢驗的抽樣程序.第5部分:按接收質量限(AQL)檢索的計量檢驗連續抽樣計劃的規范(已知標準偏差)
英文標準名稱：Sampling procedures for inspection by variables - Part 5: Sequential sampling plans indexed by acceptance quality limit (AQL) for inspection by variables (known standard deviation)
標準類型：A00
發布日期：1999/12/31 12:00:00
實施日期：1999/12/31 12:00:00
中國標準分類號：A00
國際標準分類號：03.120.30
引用標準：ISO 2859-1-1999;ISO 3534-1;ISO 3534-2;ISO 3951-1-2005
適用范圍：This part of ISO 3951 specifies a system of sequential sampling plans (schemes) for lot-by-lot inspection by variables. The schemes are indexed in terms of a preferred series of acceptance quality limit (AQL) values, ranging from 0,01 to 10, which are defined in terms of percent nonconforming items.The schemes of ISO 3951 are intended to induce a supplier through the economic and psychological pressure of lot non-acceptance to maintain a process average at least as good as the specified AQL value, while at the same time providing an upper limit for the risk to the consumer of accepting the occasional poor lot.The schemes are designed to be applied to a continuing series of lots, that is, a series long enough to allow the switching rules (Clause 6) to be applied. These switching rules provide:— automatic protection to the consumer (by means of a switch to tightened inspection or discontinuation of sampling inspection) should a deterioration in quality be detected;— an incentive (at the discretion of the responsible authority) to reduce inspection costs (by means of a switch to reduced inspection) should consistently good quality be achieved.This part of ISO 3951 is designed for use under the following conditions:a) where the inspection procedure is to be applied to a continuing series of lots of discrete products all supplied by one producer using one production process. If there are different producers or production processes, apply this part of ISO 3951 to each one separately;b) where only a single quality characteristic, x, of these products is taken into consideration, which must be measurable on a continuous scale;c) where the uncertainty of the measurement system is negligible with respect to the production process standard deviation;d) where production is stable (under statistical control) and the quality characteristic, x, is distributed according to a normal distribution (or a close approximation to the normal distribution) or a distribution which may be mathematically transformed to a normal distribution;e) where the standard deviation of the quality characteristic, x, is known;CAUTION — The procedures in this part of ISO 3951 are not suitable for application to lots that have been screened previously for nonconforming items.f) where a contract or standard defines an upper specification limit, U, a lower specification limit, L, or both; an item is qualified as conforming if and only if its measured quality characteristic, x, satisfies the appropriate one of the following inequalities: