Process Stability & Sampling - Can Sampling detect an Unstable Process?

Bev D

Heretical Statistician
Staff member
Super Moderator
#11
I think the answer comes down to a confusion on what the AQL means and how you ask the question.

An AQL is the Acceptable Quality Level; the defect rate that will not be detected and therefor will be ACCEPTED 95% of the time (typically its 95%)

An RQL (traditionally referred to as the LTPD - Lot Tolerance Percent Defective) plan will provide you a sample plan that will detect and therefor REJECT a lot that is the RQL rate or worse. So if I want to detect a defect rate of .65% with 95% confidence and I use a 'accept on zero defects' plan my sample size is: 460

Confusion about the meaning of the AQL is rampant...
 
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