用不合格品率的变量检验序贯抽样方案(适用于标准差已知的情形

[中文适用范围]： 本国际标准规定了离散项目变量检验的顺序抽样方案和程序。这些方案根据生产者风险点和消费者风险点编制索引。因此，它们不仅适用于验收抽样，也适用于更普遍的比例简单统计假设检验。本国际标准的目的是提供顺序评估检验结果的程序，这些程序可用于促使供应商供应具有高验收概率的质量批次。同时，消费者受到规定的接受劣质批次（或工艺）概率上限的保护。本国际标准主要设计用于以下情况：a) 检验程序适用于由一个生产商使用一种生产工艺供应的一系列连续的离散产品批次。在这种情况下，特定批次的抽样相当于工艺的抽样。如果有不同的生产商或生产工艺，则本国际标准应分别适用于每个生产商或生产工艺； b) 只考虑这些产品的单个质量特性 x，且该特性必须是连续可测量的； c) 测量误差可以忽略不计（即标准差不超过过程标准差的 10％）； d) 生产稳定（在统计控制下），而且质量特性 x 具有已知的标准差，并且服从正态分布或接近正态分布； 注意——本国际标准中的程序不适用于先前已筛选出不合格品的批次。 e) 合同或标准定义了规格上限 U、规格下限 L 或两者；当且仅当测得的质量特性 x 满足下列不等式中的相应一个时，某个品项才被认定为合格： 1) x ≤ U（即不违反规格上限）； 2) x ≥ L（即不违反规格下限）； 3) x ≤ U 且 x ≥ L（即，既不违反上限也不违反下限。）不等式 1）和 2）称为“单规格限值”的情况，不等式 3）称为“双规格限值”的情况。在本国际标准中，假定在适用双规格限值的情况下，符合两个规格限值对于产品的完整性同样重要，或者对于两个规格限值分别考虑。在第一种情况下，控制两个规格限值之外的产品总百分比是适当的。这称为联合控制。在第二种情况下，分别控制超出每个限值的不合格情况，这称为单独控制。 1  [外文原描述]： This International Standard specifies sequential sampling plans and procedures for inspection by variables of discrete items. The plans are indexed in terms of producer's risk point and the consumer's risk point. Therefore, they are suitable not only for the purposes of acceptance sampling, but for the more general purpose of the testing of simple statistical hypotheses for proportions. The purpose of this International Standard is to provide procedures for the sequential assessment of inspection results that may be used to induce the supplier to supply lots of a quality having a high probability of acceptance. At the same time, the consumer is protected by a prescribed upper limit to the probability of accepting a lot (or process) of poor quality. This International Standard is primarily 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. In such a case, sampling of particular lots is equivalent to the sampling of the process. If there are different producers or production processes, this International Standard shall be applied 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 measurement error is negligible (i.e. with a standard deviation no more than 10 % of the process standard deviation); d) where production is stable (under statistical control) and the quality characteristic x has a known standard deviation, and is distributed according to a normal distribution or a close approximation to the normal distribution; CAUTION — The procedures in this International Standard are not suitable for application to lots that have been screened previously for nonconforming items. e) 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: x ≤ U (i.e. the upper specification limit is not violated); x ≥ L (i.e. the lower specification limit is not violated); and (i.e. neither the upper nor the lower specification limit is violated.) Inequalities 1) and 2) are called cases with a "single specification limit", and 3) is the case with "double specification limits". In this International Standard, it is assumed that, where double specification limits apply, conformance to both specification limits is either equally important to the integrity of the product or is considered separately for both specification limits. In the first case, it is appropriate to control the combined percentage of product outside the two specification limits. This is referred to as combined control. In the second case, nonconformity beyond each of the limits is controlled separately, and this is referred to as separate control.