TS 2756-6 ISO 8423

TS 2756-6 ISO 8423 is a standard for sequential sampling plans used in inspection by variables when the decision criterion is percent nonconforming and the process standard deviation is known. In practical terms, it supports acceptance inspection based on measured characteristics rather than simple pass/fail counting, so quality decisions can be made from statistical evidence derived from variable data.

How sequential sampling works in variable inspection

Sequential sampling is a statistical decision method in which each additional observation can change the outcome to accept, reject, or continue sampling. Instead of fixing the sample size in advance, the plan uses cumulative measurement results to judge whether the lot appears acceptable. In this standard’s technical context, the known standard deviation is an important parameter because it allows the sampling limits to be defined from a stable measure of process spread.

Percent nonconforming as a decision basis

Inspection by variables uses actual measurements such as dimensions, mass, strength, or other quantifiable characteristics. Percent nonconforming refers to the estimated proportion of items outside the specification limits. This makes the method especially useful when measurement data are more informative than attribute counts, because the plan can infer lot quality from the distribution of values rather than only from the number of defective items. The standard therefore sits within the broader field of statistical acceptance sampling for measurable quality characteristics.

• The scope covers sequential sampling plans for inspection by variables based on percent nonconforming.
• The method assumes a known standard deviation for the measured characteristic.
• It provides a statistical framework for acceptance decisions using variable data.
• This listing represents the TS 2756-6 edition published as equivalent to ISO 8423:1991.