Every chair matched the sample. The batch did not.
Illustrative example This case is written from the patterns we see in furniture export orders, and the figures are representative rather than from a specific client file. It shows how a check works and what it finds. We will replace it with a real, anonymised case as soon as we can publish one with the buyer's permission.
The situation
A UK retailer ordered 480 dining chairs in a mid-oak finish. The approved sample was approved in March. Production ran across three weeks with two shifts.
The shift change mid-production was accompanied by a lacquer mix re-adjustment. Both mixes were within the factory's own tolerance. Neither was out of specification.
They were simply not the same.
Why per-unit inspection misses it
The inspector checked 80 units. Each was compared against the approved sample. Every one passed.
Then samples were taken from the front, middle and rear of the batch and compared **with each other**, side by side under daylight and again under raking light. Two of the three samples were visibly lighter.
Measured against a grey scale, the difference between the two batches was 3. The specification required 4.
| Position in the batch | Grey-scale reading |
|---|---|
| Front of batch | 4 — matches the approved sample |
| Middle of batch | **3 — measurably lighter** |
| Rear of batch | **3 — measurably lighter** |
The structural problem
**The failure is in the batch, not in any individual unit.** This is why colour cannot be checked one chair at a time against a sample.
A per-unit check answers: *does this chair match the sample?* A batch check answers: *are all the chairs in this container the same?*
Both are needed. Only the second one catches this defect.
What to put in the specification
State a **grey-scale value**, not a description. "Even colour throughout" is not checkable. "Grey scale 4 or better, measured on samples drawn from the front, middle and rear of the batch" is checkable, and it forces the check to happen.
If your order is large enough for more than one production shift, say so at booking. It changes the sampling plan.
Where to go next
Have an order you need verified? Send us your PI and factory address. Three levels, published prices, $149 per man-day from.