This International Standard describes the basis of sampling plans for the inspection by variables of milk and milk products. It is intended primarily for use under the following conditions : a) where the inspection procedure is to be applied to a continuous series of lots of discrete products, all supplied by one producer using one production process; b) where only a single quality characteristic, x, which must be measurable on a continuous scale, is taken into consideration (if several such characteristics are of importance, this International Standard applies to each of them separately); c) where production is stable (under statistical control) and the quality characteristic, x, is distributed according to a normal distribution law or a close approximation to the normal distribution law; d) where a contract or specification defines an upper specification limit U, a lower specification limit L, or both. NOTE — The product is qualified as complying with the requirements of the contract or specification if the measured quality characteristic, x, satisfies one of the following conditions : x ≤ U (1) or x ≥ L (2) or x ≤ U and x ≥ L (3) Conditions (1) and (2) are called cases with a single specification limit and condition (3) a case with double specification limits. This International Standard does not apply in the case of examination for microbiological defects.