From: Stan Hilliard shilliard@samplingplans.com
Date: 17 Sep 2002
Time: 14:21:23
The automatic detection/removal device is part of the process - from the standpoint of the sampling plan. The incoming lot to the plan has already had the detection/removal applied.
The only AQL is the AQL of the sampling plan. AQL is best viewed as a statistical property of the sampling plan rather than a property of the product. It (along with the rest of the oc curve) defines ability of the sampling plan for surveillance and decision about the lot quality at the point where the sample is taken.
Here are some definitions to distinguish between the true quality of the process lot (p') and the AQL of the sampling plan:
p' = the true fraction defective of a lot. It is estimated by the sample (pBar).
AQL = A value of fraction defective, WHICH IF TRUE FOR A LOT, would make the probability of passing that lot with that sampling plan equal to (1-alpha).
Even if the automatic detection and removal device were perfect and capable of eliminating all defectives, the AQL and oc curve of the sampling plan retain their statistical values. www.samplingplans.com/usingoccurves.htm
Stan Hilliard