(1) The process relating to gathering process data and analyzing the data to determine whether the process exhibits nonrandom variation.
(2) Broadest term used for the control of quality of a product by whatever methods are available. It includes instrument feedback loops, performance measurement and comparison to standards and responses based on that information and experience.
Quality control, or QC for short, is a process by which entities review the quality of all factors involved in production. This approach places an emphasis on three aspects:
1. Elements such as controls, job management, defined and well managed processes, performance and integrity criteria, and identification of records
2. Competence, such as knowledge, skills, experience, and qualifications
3. Soft elements, such as personnel integrity, confidence, organizational culture, motivation, team spirit, and quality relationships.
The quality of the outputs is at risk if any of these three aspects is deficient in any way.
Quality control emphasizes testing of products to uncover defects and reporting to management who make the decision to allow or deny product release, whereas quality assurance attempts to improve and stabilize production (and associated processes) to avoid, or at least minimize, issues which led to the defect(s) in the first place. For contract work, particularly work awarded by government agencies, quality control issues are among the top reasons for not renewing a contract.