Nonconformity (quality)

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In quality management, a nonconformity (sometimes referred to as a non conformance or nonconformance or defect) is a deviation from a specification, a standard, or an expectation. Nonconformities or nonconformance can be classified in seriousness multiple ways, though a typical classification scheme may have three to four levels, including critical, serious, major, and minor.[1][2][3][4]

While some situations allow "nonconformity" and "defect" to be used synonymously, some industries distinguish between the two; a nonconformity represents a failure to meet an intended state and specification, while a defect represents a failure to meet fitness for use/normal usage requirements.[2] This can be seen in the international software engineering standard ISO/IEC 25010 (formerly ISO/IEC 9126), which defines a nonconformity as the nonfulfillment of a requirement and a defect as the nonfulfillment of intended usage requirements.[5]

Classifying nonconformity[edit]

When ensuring quality of a product or a service, classification of a nonconformity is important, as it provides an opportunity to better reduce nonconformity.[1] Many quality management practices will do this using a relatively simple three- or four-level classification system.[2][4] For example, U.S. federal agencies such as the National Aeronautics and Space Administration have used a simple three-tier system for quality requirements of government-acquired supplies and services: minor, major, and critical nonconformance.[6] However, some industries may develop their own, custom ranking systems. An example from the automotive industry uses a 10-point system for finer granularity, where, for example, a one represents "none" (no effect), a six "moderate" (vehicle or item operable, but comfort or convenience items inoperable), and a 10 "hazardous without warning" (when a potential failure mode affects safe vehicle operation without warning).[1] Regardless of size, these classification schemes exist to help drive discovery and correction of nonconformities (and defects).[1][4]

Sources of nonconformity[edit]

The causes of nonconformities are not unlimited and therefore determinable. Common causes for deficiencies to arise include:[1]

  • poor communication (or miscommunication)
  • poor documentation (or lack of documentation)
  • poor or limited training of personnel
  • poor motivation of personnel
  • poor quality materials (or lack of appropriate materials)
  • poor quality tools and equipment (or lack of appropriate tools and equipment)
  • poor or dysfunctional operating environment


  1. ^ a b c d e Hoyle, D. (2009). "36. Corrective Action". ISO 9000 Quality Systems Handbook: Using the Standards as a Framework for Business Improvement. Routledge. pp. 687–704. ISBN 9781856176842.
  2. ^ a b c Berger, R.W.; Benbow, D.W.; Elshannawy, A.K.; Walker, H.F., eds. (2007). "Chapter 22 B. Material Control". The Certified Quality Engineer Handbook. ASQ Quality Press. pp. 183–189. ISBN 9780873897006.
  3. ^ Dorf, R.C., ed. (1998). The Technology Management Handbook. CRC Press. pp. 13-34. ISBN 9780849385773.
  4. ^ a b c Mitra, A. (2016). "Chapter 8: Control Charts for Attributes". Fundamentals of Quality Control and Improvement. John Wiley & Sons. ISBN 9781118705445.
  5. ^ "ISO/IEC 25010:2011 Systems and software engineering -- Systems and software Quality Requirements and Evaluation (SQuaRE) -- System and software quality models". International Organization for Standardization. March 2011. Retrieved 22 February 2018.
  6. ^ "Federal Acquisition Regulation" (PDF). General Services Administration. March 2005. p. 46.103. Retrieved 22 February 2018.