BS ISO 3951-1:2013 pdf free.Sampling procedures for inspection by variables Part 1: Specification for single sampling plans indexed by acceptance quality limit (AQL) for lot-by-lot inspection for a single quality characteristic and a single AQL. 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; b) where only a single quality characteristic, x, of these products is taken into consideration, which must be measurable on a continuous scale; c) where production is stable (under statistical control) and the quality characteristic, x, is distributed according to a normal distribution ora 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 and only if its measured quality characteristic,x, satisfies the 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….

ISO 3951-4-2011 pdf free.Sampling procedures for inspection by variables – Part 4: Procedures for assessment of declared quality levels. This part of ISO 3951 establishes sampling plans and procedures by variables that can be used to assess whether the quality level of an entity (lot, process, etc.) conforms to a declared value. The sampling plans have been devised so that their operating characteristic curves match those of the corresponding attributes plans in ISO 2859-4 as closely as possible, so that the choice between using sampling by attributes and sampling by variables is not influenced by attempts to increase the chance of accepting an incorrectly declared quality level. In this part of ISO 3951, there is a risk of between 1,4% and 8,2% of contradicting a correct declared quality level. The risk is 10 % of failing to contradict an incorrect declared quality level which is related to the limiting quality ratio (see Clause 4). Sampling plans are provided corresponding to three levels of discriminatory ability, and for the cases of unknown and known process standard deviation, In contrast to the procedures in the other parts of ISO 3951, the procedures in this part of ISO 3951 are not applicable to…