Sampling and AQL: How a Uniform Lot Gets Accepted or Rejected

Why sampling exists

Checking every metre of every roll on a program order is not practical, and a buyer cannot reject a whole lot for one flaw. A sampling plan gives both sides a fair rule: look at a set number of units picked at random, count the defects, and compare with a limit agreed in advance. If the count is within the limit, the lot is accepted. If not, it is rejected or re-inspected.

The rule is useful only if it is fixed before the order. A buyer who sets the plan after seeing a problem is not sampling, they are choosing a result. Put the plan into the purchase terms, alongside the remedies in fabric delivery claims and remedies.

Fabric rolls and finished garments use different checks

For rolls of cloth, the usual check is the four-point system, which scores defects per length. An AQL plan counts defective units, so it fits finished garments, packs and cartons better. Programs often use both: the four-point score on the cloth, then an AQL plan on the stitched uniforms. Agree which applies to which stage so a result is not judged by the wrong rule.

Defect classes

Defects are not equal, so the plan counts them in classes, each with its own limit.

The tolerances above are common conventions in apparel, not rules. The contract should state the classes, what counts in each, and the limits, so the inspector does not decide on the day.

Reading a sampling plan

An AQL plan comes from published tables, most often ISO 2859-1. You start with the lot size, find the sample size letter for the inspection level, and read off the sample size. For each AQL you then get two numbers: an accept number, the most defects you can find and still pass, and a reject number, the count at which the lot fails.

For example, under general inspection level II a lot of between 1,201 and 3,200 pieces calls for a sample of 125. At an AQL of 2.5 the table gives an accept number of 7 and a reject number of 8. So if 7 or fewer major defects are found in the 125 pieces the lot is accepted, and at 8 or more it is rejected. Check the figures against the standard itself before you write them into a contract, since the tables change with the inspection level and the edition.

What a reject triggers

Decide in advance what happens on a reject. Common outcomes are a full sort by the supplier, a re-inspection by the buyer, replacement of the defective pieces or, for a serious failure, return of the lot. Name who pays for the sort and the re-inspection, and the time allowed. A plan with no consequence is only a measurement.

Keep the sample random and drawn from across the lot, not from the top cartons, or the result tells you about the easy-to-reach pieces. Our guide to inspecting uniform fabric on delivery covers how to draw and record the sample.

FAQ

Frequently asked questions

What does AQL mean?

Acceptable quality limit. It is the worst level of defects a buyer will accept as a normal average in a lot, and it is used with a sampling plan to decide whether to accept or reject the lot.

Does passing AQL mean the lot has no defects?

No. It means the defects found in the sample were within the agreed limit. A lot that passes can still contain some defective pieces.

Is AQL used for fabric rolls?

Rolls are usually checked with the four-point system, which scores defects by length. AQL counts defective units and fits finished garments and packs better. Many programs use both at different stages.

What are critical, major and minor defects?

Critical defects make an item unsafe or unusable and are normally not tolerated at all. Major defects would cause a buyer to reject the item. Minor defects are cosmetic and do not affect use. Each class has its own limit.

Who decides the AQL level?

The buyer and supplier agree it in the contract before the order. Setting it after a problem appears turns sampling into an argument.