Instead of a 1.0% defect rate for AQL it would need to less for one of the Reject 8 specifications try 0.125 so that the tally of failure rates across the various specification of interest (assuming the possibility of failing any specifications is equal). When independent you would need separate draws of samples for each defect of interest, then apply the Accept 7/Reject 8 criteria judging only the one specification.In practice, if you want to inspect for isolated specifications, one should allocate the acceptable AQL and LPTD points and develop your sampling plan from there. #Ansi asq z1 9 2008 pdf how toWhen not independent I’m not sure how to adjust the sample size to a present the same AQL protection. If the AQL 1.0 is suitable for the specific defects, then considering them separate for the 8 criteria would no longer be an overall ASQ 1.0 protection it would be much less.Your example of 56 defects being accepted underscores the point that the AQL protection is no longer 1.0.I’m assuming the specifications and causes of the defects are independent, yet that may not be the case. This is further supported by any item with one of the many specifications out of range would be deemed a failure.On the other hand, if the lot sampling is to detect lots with specific faults, isolated to a specific specification then the defect types would be considered separately. If they want to know if individual units within the lot are acceptable – based on all criteria that is considered acceptable, then the tally of all defects found is correct. The vendor’s interpretation is that each of the items within the major category should have an accept / reject allowance of 7 / 8 (so potentially, in this case, 56 defects would still be accepted).Can you please forward my question onto a suitable SME at ASQ for help with this matter? Please let me know if you need any further information or clarification.Thank you again.Response:In this case, it depends on the question the lot sampling is trying to answer. 3 that fail outer diameter, 3 that fail height of the bottle finish and 3 that fail weight – total of 9 – would constitute a rejection of the lot). We have a number of different defects that fall into an AQL of 1.0.Please note that the same question applies to all AQL levels, as our critical and minor defects can also have multiple defects.Our interpretation of the standard is that if the sampling plan table (based on sample size and inspection level) shows Accept 7 / Reject 8 then all defects in this major category would be cumulative for the accept / reject criteria. Question:We are having an interpretation issue regarding the ANSI/ASQ Z1.4:2008 standard with some of our component vendors. If this failure falls within the 5%, your process is working and while you sort through the lot, and notify the supplier, it is not something that you over react to.I hope this helps.JimJames Bossert, PhD, MBB, CQA, CQE, CqM/OESr Performance Improvement Consultant Author Posted on Categories, Tags. That is the pure definition of the alpha risk. Once that confidence is restored, then you go back to what you inspected originally.The second question, is one that you have to understand how well do you follow the acceptance sampling process? If your alpha level is at 95%, 5% of the time, you can accept a bad batch as good. That way you can estimate the% defective and if another failure occurs in the next 5 lots, then increase the sampling until you have some confidence that the supplier has fixed the problem. I have two questions.If I have one lot that fails Acceptance sampling and I am trying to bound the issue is it suitable to bound it to the one affected lot if the lot before and after pass or do I need to carry out additional sampling.My second question is if I have a batch that passes acceptance sampling but at a subsequent downstream process a defect being inspected for by the upstream acceptance sampling inspection is found how do I determine if the lot is acceptable? Do I trust the acceptance sampling inspection or react?AnswerThe first question is not an uncommon one and actually it is a good practice to isolate the lot and do 100% inspection of it. We do not uses switching rules as we have always found them too difficult to manage. QuestionWe have an Acceptance sampling inspection in place where we use the ANSI/ASQ Z1.4 – 2013 standard under Normal Inspection, using General Inspection Level II to drive our samples size and accept, reject criteria.
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