BS ISO 3951-1:2022 - TC

What is BS ISO 3951-1:2022 Sampling procedures for inspection by variables about?

This document is the first in a multi-part series that applies statistical methods to sampling in order to control the acceptance of quality products.  ISO 3951-1:2022 details sampling plans indexed by acceptance quality limit with inspection for a single quality characteristic.

Who is ISO 3951-1:2022 Sampling procedures for inspection by variables for?

• Any organization purchasing or selling items where there is a need to stay within specification limits

What does ISO 3951-1:2022 Sampling procedures for inspection by variables cover?

ISO 3951-1 specifies single sampling plans for lot-by-lot inspection under the following conditions:

1. Where the inspection procedure is applied to a continuing series of lots of discrete products all supplied by one producer using one production process
2. Where only a single quality characteristic, x, of these products is taken into consideration, which must be measurable on a continuous scale
3. 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
4. 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 ≥ L (i.e., the lower specification limit is not violated)
• x ≤ U (i.e., the upper specification limit is not violated)
• x ≥ L and x ≤ U (i.e. neither the lower nor the upper specification limit is violated)

The first two inequalities are called cases with a single specification limit, and the third a case with double specification limits.

Where double specification limits apply, it is assumed in ISO 3951-1 that conformity 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 a product outside the two specification limits. This is referred to as combined control.

Why should you use BS ISO 3951-1 Sampling procedures for inspection by variables?

• This standard uses switching rules to ensure that lots of acceptable quality have a high probability of acceptance, while the probability of not accepting inferior lots is as high as practicable

• BS ISO 3951-1 thus enables users to improve sampling efficiency and reduce risk at the same time, both protecting consumers and your brand

• BS ISO 3951-1 is suitable for users with simple requirements

The 2022 update includes informative software that supports implementation of the acceptance tests and produces information that was previously found in tables and diagrams.

BS ISO 3951-1:2022 contributes to UN Sustainable Development Goal 9 on industry, innovation and infrastructure and Goal 12 on responsible consumption and production.

What’s new about BS ISO 3951-1:2022?

This is a revision of ISO 3951-1:2013. The major changes in BS ISO 3951-1:2022 are:

1. Procedures have been introduced to accommodate measurement uncertainty

2. Many sampling plans have been adjusted to improve the match between their operating characteristic curves and the operating characteristic curves of the corresponding plans for single sampling by attributes in BS ISO 2859-1

3. There are major changes to the layout of the standard, with many tables and diagrams removed

4. Recommended informative software is now available to download that supports the use of the standard and produces information previously available in tables and diagrams