TS ISO 8423

TS ISO 8423 is the standard for sequential sampling plans used in inspection and test when a measurable characteristic is assessed in terms of percentage non-compliance, with the standard deviation assumed to be known. In this type of acceptance sampling, the decision is built up step by step from accumulating evidence rather than from a fixed sample size, which is especially relevant when the process is stable and the quality characteristic can be tracked through a single numerical measurement.

How sequential plans work in practice

In a sequential plan, each new observation is added to the running total that leads toward acceptance or rejection. This can allow the inspection to stop earlier than in a single-stage plan. The approach is commonly associated with measurable characteristics and distribution-based evaluation, where quality is judged against an upper limit, a lower limit, or both. The key technical distinction is that the item is assessed by measurement, and the process variation is treated through a known standard deviation.

Defined use conditions covered by this standard

• Continuing series of lots of discrete items from one producer and one production process.
• Evaluation based on a single quality characteristic x.
• A stable production process with known standard deviation for x.
• An upper limit, a lower limit, or both being specified.
• A complementary relationship to ISO 8422.

In general statistical quality control, sequential sampling helps balance producer and consumer risks while avoiding more inspection than necessary. It is widely used where decisions need to be made from measured data rather than simple conforming/nonconforming checks. TS ISO 8423 provides this concept for measurable characteristics under known variability; the detailed procedures, decision rules, and calculations belong to the standard itself.