How Do Product Inspections Treat Defects?

Alex Davies says the inspection process for most regular products that are not life and death, like a shirt or a piece of Ikea furniture, is set up to let a certain number of defective products through. The allowance might be something like 5 percent bad, and for clothes maybe 10 percent. A 50 percent defect rate is a financial problem. A 2 percent defect rate is one a company can probably get away with.

Statistical tables say how many items to test to hit a chosen defect rate, and defects come in levels. Spider-Man pajamas with Superman on them are a fundamental defect, and even one is probably enough to reject the entire lot. One leg slightly longer than the other on two out of 100 is a minor defect that might pass. Actuaries inside the companies work out how many defects they can allow before throwing out the lot costs more than dealing with angry customers, and the cutoff is just math. A screw that does not line up where it had to be is probably a minor defect, the sort of 2 percent case already expected, so one bad review is a weak sign the whole run failed. People write more negative reviews than positive reviews.