How to read Ac and Re
In the ISO 2859-1 sampling table, the code letter picks the row and the AQL picks the column. The cell holds two numbers, written as Ac / Re, for example 5 / 6.
- At or below Ac: that defect class passes.
- At or above Re: that defect class fails, and with it the lot.
The classes are not added together. In a sample of 125 with limits of 7 / 8 for major and 10 / 11 for minor, four major and nine minor defects pass, because each count is below its own Re. But one class reaching its Re is enough to fail the lot. Critical defects usually run at accept 0, reject 1.
Example from a real inspection
Our Sample 04 report covered 661 pieces of wood, iron and marble furniture in Jodhpur. At general level II the lot takes code letter J, a sample of 80 pieces. The plan was:
| Class | AQL | Ac / Re | Found | Result |
|---|---|---|---|---|
| Critical | 0 | 0 / 1 | 0 | Pass |
| Major | 2.5 | 5 / 6 | 8 | Fail |
| Minor | 4.0 | 7 / 8 | 6 | Pass |
Eight major defects, mostly cracks in wood and marble, passed the reject number of 6. The lot was Not cleared even though the minor count was within its limit.
Count defects or defective units?
One unit can carry several defects. Agree before the inspection whether the inspector counts each defect, or each defective unit once under its most serious defect. ISO 2859-1 allows both: the AQL is then read as percent nonconforming units or as nonconformities per 100 units, two ways of stating a defect rate. Near the limit, the choice can change the result. Clear To Load writes the counting rule and the Ac / Re pairs into the checklist before the visit, so the factory and you read the report the same way. The AQL calculator gives the pairs for any lot.