ISO 3951-2

Description / Abstract: This part of ISO 3951 is primarily designed for use under the following conditions:

a) 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. If there are different producers or production processes, this part of ISO 3951 shall be applied to each one separately;

b) where the quality characteristics of the items of product are measurable on a continuous scale;

c) where the measurement error is negligible (i.e. with a standard deviation no more than 10 % of the corresponding process standard deviation). However, procedures are also provided in Clause 9 and Annex P for accommodating measurement error when it has a non-negligible standard deviation;

d) where production is stable (under statistical control) and the quality characteristics are distributed, at least to a close approximation, according to normal distributions;

e) where, in the case of multiple quality characteristics, the characteristics are independent, or almost independent, of one another;

f) where a contract or standard defines a lower specification limit, L, an upper specification limit, U, or both on each of the quality characteristics.