ISO 3951-1:2005 Sampling procedures for inspection by variables - Part 1: Specification for single sampling plans indexed by acceptance quality limit (AQL) for lot-by-lot inspection for a single quality characteristic and a single AQL
This part of ISO 3951 specifies an acceptance sampling system of single sampling plans for inspection by
variables, in which the acceptability of a lot is implicitly determined from an estimate of the percentage of
nonconforming items in the process, based on a random sample of items from the lot.
This part of ISO 3951 is primarily designed for application 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;
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 is distributed
according to a normal distribution or a close approximation to the normal distribution;
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:
1) x W L (i.e. the lower specification limit is not violated);
2) x u U (i.e. the upper specification limit is not violated);
3) x W L and x u U (i.e. neither the lower nor the upper specification limit is violated).
Inequalities 1) and 2) are called cases with a single specification limit, and 3) a case with double specification
limits.
If double specification limits apply, it is assumed in this part of ISO 3951 that conformance to both
specification limits is equally important to the integrity of the product; in such cases it is appropriate to apply a
single AQL to the combined percentage of product outside the two specification limits. This is referred to as
combined control.
ISO 3951-1:2005 history
2022ISO 3951-1:2022 Sampling procedures for inspection by variables — Part 1: Specification for single sampling plans indexed by acceptance quality limit (AQL) for lot-by-lot inspection for a single quality characteristi
2013ISO 3951-1:2013 Sampling procedures for inspection by variables.Part 1: Specification for single sampling plans indexed by acceptance quality limit (AQL) for lot-by-lot inspection for a single quality characteristic and a single AQL
2005ISO 3951-1:2005 Sampling procedures for inspection by variables - Part 1: Specification for single sampling plans indexed by acceptance quality limit (AQL) for lot-by-lot inspection for a single quality characteristic and a single AQL