ISO 28590:2017 pdf free

ISO 28590:2017 pdf free.Sampling procedures for inspection by attributes
Sampling based on experience with the product, the process, the producer and the consumer can be statistically evaluated, provided that random sampling and a predefined set of rules for varying sample size and sampling frequency are used.
An example is the procedure described in ISO 2859-1, which uses a set of switching rules. When the quality is very good, it is possible to switch to reduced inspection. This provides a procedure where,if smaller samples are used, the producer’s risk is reduced but the consumer’s risk is increased. If the process average is consistently smaller than the specified acceptance quality limit (AQL), this is justified. When the process average over at least 10 lots has been very much smaller than the AQL, some consumers resort to skip-lot procedures (see ISO 2859-3). This can be even more economical than the reduced inspection described in ISO 2859-1.
In some instances, particularly when routine or non-critical items are involved, some consumers may feel safe in resorting to the practice of inspecting small samples of the product and, provided there are zero nonconforming items, accepting the lot. For example, a sample size of eight with an acceptance number of zero is equivalent to the small lot sampling plans with an AQL of 1,5 % normal, or 0,65 % reduced inspection. See Tables 2-A and 2-C in ISO 2859-1:1999.
Conversely, in ISO 2859-1, when two out of five or fewer successive lots fail inspection, normal inspection is discontinued and tightened inspection is instituted. Once tightened inspection has been instituted, normal inspection is not restored until five successive lots have been accepted on tightened inspection. This requirement is intentionally severe, because evidence of unacceptable quality has been found, as a result of which, the producer forfeits the right to the benefit of the doubt. If, while operating on tightened inspection, the cumulative number of lots not accepted on original tightened inspection reaches five, inspection by sampling shall be discontinued until there is evidence that corrective action has been taken and has been fully effective.ISO 28590 pdf download.