Tools for controlling quality: What is done prior to production, as well as thereafter, is as important as the production process itself in ensuring the quality of products

In the Middle Ages, skilled craftsmen worked long years as apprentices under the watchful eyes of journeymen and masters before they were prepared to produce quality products. But with the introduction of interchangeable parts by Eli Whitney at the beginning of the 19th century, new methods of quality control were required. First piece-part measurements, then inspections and statistical sampling techniques, were introduced. By World War II, modern methods of quality control were established, and in the past four decades these have changed relatively little.