计量检验的抽样程序.第3部分:按接收质量限(AQL)检索的逐批检验二次抽样计划

[中文适用范围]： ISO 3951 的这一部分规定了双重抽样方案的验收抽样系统，用于通过变量检查不合格百分比。 它以验收质量限度 (AQL) 为索引。 ISO 3951 本部分规定的方法的目标是确保可接受质量的批次具有较高的接受概率，并且不接受劣质批次的概率尽可能高。 这是通过转换规则实现的，该规则为消费者提供——如果检测到质量恶化，自动保护消费者（通过转换为更严格的检验或中止抽样检验）；以及——激励措施（由消费者自行决定）主管当局）以降低检验成本（通过切换到较小的样本量）应始终获得良好的质量。 在 ISO 3951 的这一部分中，批次的可接受性是根据批次中的一个或两个随机样本对过程中不合格品百分比的估计来隐式或显式确定的。 ISO 3951 的这一部分主要设计用于以下条件： a) 检验程序适用于由一个生产商使用一个生产流程供应的一系列连续批次的离散产品；如果有不同的生产商或生产工艺，则分别适用 ISO 3951 的本部分； b) 产品具有单一质量特性（对于多种质量特性，参见资料性附录 A、B 和 C）； c) 质量特性可以连续测量； d) 测量误差可以忽略不计（即标准偏差不超过相应过程标准偏差的10%）； e) 产量稳定（在统计控制下）并且质量特性的分布至少接近正态分布；注意 — ISO 3951 本部分中的程序不适用于之前已筛选出不合格品的批次。 f) 如果必须选择和检查第二个样品的可能性在管理上是可接受的； [外文原描述]： ISO 3951-3:2007 specifies an acceptance sampling system of double sampling schemes for inspection by variables for percent nonconforming. It is indexed in terms of the acceptance quality limit (AQL). The objectives of the methods laid down in ISO 3951-3:2007 are to ensure that lots of acceptable quality have a high probability of acceptance and that the probability of non-accepting inferior lots is as high as practicable. This is achieved by means of the switching rules, which 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, and an incentive (at the discretion of the responsible authority) to reduce inspection costs (by means of a switch to a smaller sample size) should consistently good quality be achieved. In ISO 3951-3:2007, the acceptability of a lot is implicitly or explicitly determined from an estimate of the percentage of nonconforming items in the process, based on either one or two random samples of items from the lot. ISO 3951-3:2007 is primarily designed for use under the following conditions: 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; where the items of product have a single quality characteristic; where the quality characteristic is measurable on a continuous scale; where the measurement error is negligible (i.e. with a standard deviation no more than 10 % of the corresponding process standard deviation); where production is stable (under statistical control) and the quality characteristic is distributed, at least to a close approximation, according to a normal distribution; where the possibility of having to select and inspect a second sample is administratively acceptable; and where a contract or standard defines an upper specification limit, a lower specification limit, or both on the quality characteristic. The procedures in ISO 3951-3:2007 are not suitable for application to lots that have been screened previously for nonconforming items.