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Sampling Plan Analyzer Help System 

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AQL - Acceptable Quality Level

The AQL of a sampling plan is a level of quality routinely accepted by the sampling plan. It is generally defined as that level of quality (percent defective, defects per hundred units, etc.) that the sampling plan will accept 95% of the time. This means lots at or better than the AQL are accepted at least 95% of the time. The AQL can be determined using the OC curve by finding that quality level on the bottom axis that corresponds to a probability of acceptance of 0.95 (95%) on the left axis.

Associated with the AQL is a confidence statement one can make. If the lot fails the sampling plan, one can state with 95% confidence that the quality level (defective rate, etc.) exceeds the AQL. In other words, failing the sampling plan demonstrates that the AQL has been exceeded.

The probability of acceptance at the AQL can be changed using the
Definitions of AQL and LTPD dialog box. The associated confidence statements are also displayed in this dialog box.

The AQL is used to help describe the
protection provided a sampling plan. But it only provides half the answer. It describes what the sampling plan will accept. We would also like to know what the sampling plan will reject. The answer to this second question is provided by the LTPD.