They provide, under a wide range of unknowable circumstances, future and past, a rational and economic guide to minimum economic loss from both mistakes. The control chart sends statistical signals, which detect existence of a special cause (usually specific to some worker or group or to some special fleeting circumstance), or tell us that the observed variation should be ascribed to common causes, chance variation attributable to the system.

The moral is that testing may cause more trouble than the product itself. Much product is condemned falsely in industry only because of measurement processes that give answers that do not agree with other answers.

Meaning starts with the concept, which is in somebody’s mind, and only there: it is ineffable. ... An operational definition puts communicable meaning into a concept. Adjectives like good, reliable, uniform, round, tired, safe, unsafe, unemployed have no communicable meaning until they are expressed in operational terms of sampling, test, and criterion.

We drive an automobile from coast to coast under uniform traffic signals. In Chicago we buy a tire that was made in Akron, and it will fit the wheel (made in Pittsburgh) of the car (built in Detroit) that we bought in New York. ... American mass production, made possible by standardization, was our number-one weapon in World War II.