Aoq
What is the difference between AOQ and AOQL?
AOQ is the expected outgoing defect level for a given incoming quality under a sampling plan. AOQL is the maximum AOQ value over all incoming quality levels for that plan, representing the worst-case outgoing defect rate the plan can produce.
What assumptions does the AOQ calculation rely on?
It assumes rejected lots undergo 100% rectifying inspection and that defective units are removed, reworked, or replaced before the lot is released. If full screening is impossible or inspection is destructive, the rectifying assumption no longer holds.
Why is AOQ useful in procurement and supplier quality decisions?
AOQ helps compare supplier lots by estimating the quality actually entering inventory after inspection, rather than the quality declared by the supplier. It supports decisions on supplier qualification, rework queue sizing, and quarantine volume based on expected defect burden after rectification.
Average Outgoing Quality (AOQ) is the expected average fraction or percent defective in product released after sampling inspection, assuming rejected lots receive 100% rectifying inspection and defectives are removed, reworked, or replaced. AOQ depends on incoming quality, lot acceptance probability, and sample/lot size; its maximum value is the Average Outgoing Quality Limit (AOQL).
On the shop floor, AOQ comes into play whenever receiving or in-process inspection uses sampling instead of screening every unit, but rejected lots are sent back for 100% rectification before release. Quality engineers rely on AOQ to estimate how many defective purchased parts or bulk raw materials still slip into the next operation after inspection, which is critical when full inspection is too costly. In warehousing, that expected outgoing defect rate drives supplier quality decisions, rework-queue sizing, quarantine volumes, and line-side availability. If a bad lot is caught late, the defect burden entering stock directly affects inventory integrity and material flow. Technically, as incoming quality worsens or acceptance probability changes, the AOQ curve shows how much bad material remains in circulation under the plan. This metric is most meaningful for rectifying inspection systems, because full screening makes outgoing quality materially better than incoming lot quality.
False confidence from a permissive plan: A weak supplier lot can still be accepted, so AOQ underestimates defect leakage while bad parts reach stores and the line before downstream use.
Conflating AOQ with raw supplier quality: Treating AOQ as the incoming defect rate distorts PPM exposure, quarantine load, and MRP replacement demand because the metric depends on sampling and rectification.
Bottlenecked rectification ignored: Rejected lots must be fully screened, but limited receiving or rework capacity strands bad material in hold areas, delaying put-away and creating shortages despite on-hand stock.