What an AQL Inspection Report Actually Tells You
A pre-shipment inspection that says "pass" does not mean the order is defect-free. Here is how AQL sampling works, how to read the numbers in the report, and which limits to set before the inspector arrives.
In this piece 5 sections
Most importers buying from Asia rely on a pre-shipment inspection: an independent inspector visits the factory once production is finished and most of the goods are packed, opens a random sample of cartons and checks them against your specification. The report that comes back is built on AQL sampling, and it is easy to misread.
What AQL means
AQL stands for acceptance quality limit. It is the worst defect rate you are prepared to accept as a process average, expressed as a percentage. The sampling tables come from ISO 2859-1, which is essentially the same as ANSI/ASQ Z1.4 in the US. Inspectors almost always use General Inspection Level II unless you ask otherwise.
How the sample size is set
The size of your order, the lot, sets a code letter, and the code letter sets how many units are inspected. For example, at General Inspection Level II an order of 3,201 to 10,000 units gives code letter L, which means a sample of 200 units.
| Lot size | Code letter (Level II) | Sample size |
|---|---|---|
| 1,201 – 3,200 | K | 125 |
| 3,201 – 10,000 | L | 200 |
| 10,001 – 35,000 | M | 315 |
How many defects are allowed
Each defect class gets its own AQL, and the table gives an accept number and a reject number for that sample size. A common set for consumer goods is 2.5 for major defects and 4.0 for minor ones, with critical defects set to zero tolerance. With a sample of 200, that allows up to 10 major defects (11 fails the lot) and up to 14 minor defects (15 fails it).
| Sample size | AQL 1.5 (accept / reject) | AQL 2.5 | AQL 4.0 |
|---|---|---|---|
| 125 | 5 / 6 | 7 / 8 | 10 / 11 |
| 200 | 7 / 8 | 10 / 11 | 14 / 15 |
| 315 | 10 / 11 | 14 / 15 | 21 / 22 |
Critical, major, minor
Critical defects could harm a user or break the law, such as a sharp edge or a missing safety warning. Major defects make the product unsellable or likely to be returned. Minor defects are cosmetic issues a customer might accept. Write your own list for each class; inspectors classify against it.
A pass means the sample stayed under your limits. At AQL 2.5 you have agreed in advance to live with some defective units.
Reading the report
Beyond the headline pass or fail, read the sections that explain it: quantity found against quantity ordered, packing and carton markings, the defect tally by class with photos, on-site tests such as carton drop tests, barcode scans and function checks, and measurements against your specification. A "pending" result usually means something needs your judgement, such as a missing approval sample or a defect that is not on your list.
What to do when it fails
A failed inspection is a negotiation point, not the end of the order. The usual options are sorting and reworking the goods followed by a re-inspection, which the supplier should pay for, accepting with a discount, or rejecting the shipment. This is where tying the balance payment to a passed inspection pays off: the money has not moved yet.
