Description

ISO 3951-1:2005 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.

ISO 3951-1:2005 is primarily designed for application 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;

• where only a single quality characteristic x of these products is taken into consideration, which must be measurable on a continuous scale;
• where the measurement error is negligible, i.e. with a standard deviation no more than 10% of the process standard deviation;
• 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;
• 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 greater than or equal to L;
  • x less than or equal to U.