| In modern society, production process is usually continuous, so sampling inspection should also be designed to be used in continuous lot. Sometimes unqualified product rate is very low. In this cases, large number of samples will be inspected in the traditional sampling plans, which would inevitably increase the cost. That's why the sequential sampling plan was introduced to decrease the sample size. However, there was possibility that large sample size and inadequate-using historic lot might exist in the sampling plan of sequential probability ratio test (SPRT).The 2-SPRT sampling plan, proposed by Lorden in 1976, improved by Huffman in 1983, has a good nature that it owns a maximum sample size. Hence, this paper adopted it to design the normal sampling inspection plan, and also use the flat-pushing manipulation to design both tightened and reduced sampling inspection plan. The tightened sampling inspection, rejecting the batch in high possibility, should be applied to the situation with bad-quality products; while the reduced sampling inspection, decreasing the sample size, should be applied to the opposite situation.The transition rules in the standard of ISO3951.1-2005 and GB2828.1-2003 were also introduced to decide which sampling plan should be adopted in different situations. It's believed to take full use of the historic lots' testing information. Every time, this new sampling plan adopts normal 2-SPRT plan to start the sampling inspection, until the inspection results meet transition rules, then tighten/reduced 2-SPRT sampling plan will be adopted. The reduction of the sample size is able to be achieved through transition of different sampling inspection plans.. Compared with 2-SPRT, SPRT and adjusting SPRT, the average of sample size was smaller and both of risk could be better controlled through the manipulation.
|
PDF Full Text Request