(The rod from which the bolt was threaded should not have been placed into that machine if it was the wrong length, for example. The defect should have been prevented by using appropriate jigs or other manufacturing techniques. If a bolt is longer or shorter than required, it does not 'conform to requirements', and therefore is defective. The four principles are: defining quality as 'conformance to requirements' preventing defects is better than inspecting and correcting them setting 'zero defects' as the standard and that defects cost money.Īn example of the Zero Defects approach involves a fastening bolt. The program's first target was the category of large-volume, common components obtained from suppliers. 'Zero Defects' is a quality-oriented program developed in the Martin Marietta Corporation in the 1960s. TQM also tries to manage the quality of the inputs from suppliers, as well as the efforts of front-line workers and upper management. Various techniques are employed, with stress on obtaining customer involvement, even as early as the design and specification phases of product development. 'TQM' ( Total Quality Management) looks to gain a competitive edge by increased customer satisfaction as a result of improvements in quality. Some trace the roots of QA and QC to quality initiatives required by increased factory production after World War I. The term 'Quality Assurance', or QA, is often seen as an element of Quality Control the 'Assurance' comes from ongoing and systematic testing and evaluation. The discipline places its emphasis on controls, such as written procedures, management to ensure compliance with those procedures, solid record-keeping, training and certification, and elements of organizational culture to promote these disciplines.

'Quality Control', or QC, is a rather generic term.

Examples of 'quality' programs and methodologies, in development since the 1920s, include:

Six sigma history and success stories