BS ISO 3951-2:2013

Foreword
Introduction
1 Scope
2 Normative references
3 Terms and definitions
4 Symbols
5 Acceptance quality limit (AQL)
6 Switching rules for normal, tightened, and
   reduced inspection
7 Relation to ISO 2859-1 and ISO 3951-1
8 Consumer protection
9 Accommodating measurement variability
10 Planning
11 Choice between variables and attributes
12 Choice between the s-method and sigma-method
13 Choice of inspection level and AQL
14 Choice of sampling scheme
15 Preliminary operations
16 Standard procedures for the univariate s-method
17 Standard multivariate s-method procedures for
   independent quality characteristics
18 Standard univariate sigma-method procedures
19 Standard multivariate sigma-method procedures for
   independent quality characteristics
20 Standard multivariate combined s-method and
   sigma-method procedures for independent quality
   characteristics
21 Procedure during continuing inspection
22 Normality and outliers
23 Records
24 Operation of switching rules
25 Discontinuation and resumption of inspection
26 Switching between the s-method and sigma-method
Annex A (normative) - Table for determining the
        sample size code letter
Annex B (normative) - Form k single sampling plans:
        s-method
Annex C (normative) - Form k single sampling plans:
        sigma-method
Annex D (normative) - Form p* single sampling plans:
        s-method
Annex E (normative) - Form p* single sampling plans:
        sigma-method
Annex F (normative) - Values of f[s] for maximum
        sample standard deviation (MSSD)
Annex G (normative) - Values of f[sigma] for maximum
        process standard deviation (MPSD)
Annex H (normative) - Estimating the process fraction
        nonconforming for sample size 3: s-method
Annex I (normative) - Values of c[U] for upper control
        limit on the sample standard deviation
Annex J (normative) - Supplementary acceptability
        constants for qualifying towards reduced
        inspection
Annex K (normative) - Procedures for obtaining s
        and sigma
Annex L (normative) - Estimating the process fraction
        nonconforming
Annex M (informative) - Consumer's risk qualities
Annex N (informative) - Producer's risks
Annex O (informative) - Operating characteristics for
        the sigma-method
Annex P (informative) - Accommodating measurement
        variability
Bibliography

Provides the primarily designe for use, 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.

This part of ISO3951 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. If there are different producers or production processes, this part of ISO3951 shall be applied to each one separately; where the quality characteristics of the items of product are 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). However, procedures are also provided in Clause9 and AnnexP for accommodating measurement error when it has a non-negligible standard deviation; where production is stable (under statistical control) and the quality characteristics are distributed, at least to a close approximation, according to normal distributions; where, in the case of multiple quality characteristics, the characteristics are independent, or almost independent, of one another; where a contract or standard defines a lower specification limit, L, an upper specification limit, U, or both on each of the quality characteristics. If there is only one quality characteristic, an item is qualified as conforming if its measured quality characteristic x satisfies the appropriate one of the following inequalities: 1) x ≥ L (i.e. the lower specification limit is not violated); 2) x ≤ U (i.e. the upper specification limit is not violated); 3) x ≥ L and x ≤ U (i.e. neither the lower nor the upper specification limit is violated). If there are two or more, say m, quality characteristics, then, designating the lower and upper limits for the ith quality characteristic by Li and Ui respectively, an item of product is qualified as nonconforming if one or more of its m measured quality characteristics, xi, fails to satisfy the appropriate one of the following inequalities: 4) xi ≥ Li; 5) xi ≤ Ui; 6) xi ≥ Li and xi ≤ Ui. Inequalities 1), 2), 4), and 5) are called cases with a single specification limit while 3) and 6) are called cases with double specification limits. For double specification limits, a further distinction is made between combined control, separate control, and complex control. If there is only one quality characteristic, then combined control is where a single AQL applies to nonconformity beyond both limits, separate control is where separate AQLs apply to nonconformity beyond each of the limits, and complex control is where one AQL applies to nonconformity beyond the limit that is of greater seriousness and a larger AQL applies to the total nonconformity beyond both limits. If there are two or more quality characteristics, this generalizes as follows: combined control is where nonconformity beyond both limits on a variable belongs to the same class, to which a single AQL applies; separate control is where nonconformity beyond the two limits on a variable belongs to separate classes, to each of which a single AQL applies; complex control is where nonconformity beyond the limit that is of greater seriousness belongs to one class to which a single AQL applies, and the total nonconformity beyond both limits belongs to another class to which a larger AQL applies. Note that, in the case of two or more quality characteristics, nonconformity on more than one quality characteristic may belong to the same class.