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AOQL - Average Outgoing Quality Limit

The AOQL of a sampling plan is maximum value on the AOQ curve.  It is applicable for defective units, defects per unit, and defects per quantity.  It is expressed as either a defective rate (fraction defective, percent defective, dpm) or as a defect rate (defects per unit, defects per 100 units, dpm).  The AOQ curve gives the average outgoing quality (left axis) as a function of the incoming quality (bottom axis).  The AOQL is the maximum or worst possible defective or defect rate for the average outgoing quality.  Regardless of the incoming quality, the defective or defect rate going to the customer should be no greater than the AOQL over an extended period of time.  Individual lots might be worst than the AOQL but over the long run, the quality should not be worse than the AOQL.

The AOQ curve and AOQL assume rejected lots are 100% inspected, and is only applicable to this situation.  They also assume the inspection is reasonably effective at removing defectives or defects (90% effective or more).