Unnoticed Effects of Inspection Errors and a Quality Paradox

A central element of quality assurance is inspections. Inspections, however, are imperfect and prone to errors. Devastating effects of inspection error type I – rejection of conforming items, are considered in this note. When several inspections are performed along a serial process, the number of falsely rejected items is similar in magnitude to (or even larger than) the number of defective items. Moreover, to compensate for this loss, more units should enter the process and consequently, more units turn defective. The quality community seems to be unaware of these effects, certainly of the last one, despite their practical significance.