UNI ISO 3951-1:2022

This document specifies single sampling plans for lot-by-lot inspection under the following conditions: a) where the inspection procedure is 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 is measurable on a continuous scale; c) where production is under statistical control and the quality characteristic, x, is distributed according to a normal distribution or a close approximation to the normal distribution; d) where a contract or standard defines a lower specification limit, L, an upper specification limit, U, or both. An item is qualified as conforming if its measured quality characteristic, x, satisfies as appropriate one of the following inequalities: 1) x ≥ L (i.e. the lower specification limit is not violated); 2) x ≤ U (i.e. the upper specification limit is not violated); 3) x ≥ L and x ≤ U (i.e. neither the lower nor the upper specification limit is violated). Inequalities 1) and 2) are cases with a single specification limit, and 3) is a case with double specification limits.