Body of Knowledge Origins and History

The IASSC Lean Six Sigma Body of Knowledge™ is an assembly of a comprehensive set of topics and subject matters that are intended to be representations of the universally and commonly accepted, minimum competencies and core proficiencies requisite of Lean Six Sigma Black Belts, Lean Six Sigma Green Belts and Lean Six Sigma Yellow Belts.¹

These well-established IASSC Standards are diversely recognized as relevant and practical versions of the knowledge expectations of Lean Six Sigma Practitioners. They are used and recognized by hundreds of Lean Six Sigma Providers, Institutions and Practitioners.


The IASSC Lean Six Sigma Bodies of Knowledge were originally established based upon the Open Source Six Sigma (OSSS) table of contents. OSSS was, and is, an exclusive publisher of Lean Six Sigma Training materials that does not provide any Lean Six Sigma training.  As a result, no other Lean Six Sigma related entity in the industry had such wide reaching and diverse non-competitive relationships with Lean Six Sigma Training Providers and Institutions using Lean Six Sigma. Through cooperation with OSSS, IASSC was able to establish what it considers to be the practical and common minimum competency for Lean Six Sigma Practitioners. These resulting competencies were assembled as the IASSC Bodies of Knowledge, made available to the industry in 2009 and have been widely embraced ever since. IASSC does not require, nor encourage, the use of OSSS. Adoption of IASSC Bodies of Knowledge, Accreditation and / or Certification is not contingent or dependent upon use of, or any connection to, OSSS or its products. And absolutely no added or extra incentives or benefits are provided by IASSC to those who choose to use OSSS. Citation: Open Source Six Sigma Press Release. OSSS shares common parent company ownership with IASSC, view disclosure.

Lean Six Sigma Provider Alignment and Adoption

As of today, 392 Accredited Providers have elected to adopt IASSC’s published standards. Furthermore, less than 7% of these IASSC Accredited Lean Six Sigma providers use any form of OSSS materials. This is significant because it establishes that a large and diverse group of Lean Six Sigma providers align and strongly correlate with the IASSC Lean Six Sigma Body of Knowledge, even though this group did not assist in the initial establishment of the IASSC Lean Six Sigma Body of Knowledge. This fact further demonstrates the accuracy of the IASSC Lean Six Sigma Body of Knowledge as the relevant minimum competency standard in the industry. Citation: IASSC Accredited Providers

Comparison to other recognized standards

IASSC conducts ongoing reconciliations and comparisons against the published criteria defined by other well-recognized institutions that operate within the Lean Six Sigma Industry, such as the American Society for Quality (ASQ) and the International Organization for Standardization (ISO).

Naturally differences do exist in our standards; however, almost all of the topics contained within the IASSC Lean Six Sigma Body of Knowledge can be found as an integral part of each of these other standards. The ASQ Body of Knowledge (BoK) defines areas outside of what IASSC believes the industry considers standard knowledge requirements for the designated belt.  These areas include Enterprise Wide Deployment and DFSS, among others. However, the Define, Measure Analyze, Improve and Control (DMAIC) components of the IASSC & ASQ BoKs are almost identical. These facts further demonstrate the accuracy of the IASSC Lean Six Sigma Body of Knowledge as the relevant minimum competency standard in the industry.

Broad Industry Feedback & Survey 

IASSC works hard on a daily basis to promote Certification Best Practices in the Lean Six Sigma Market and we are proud to be trusted as a recognized authority. We welcome and value your feedback, please take this opportunity to weigh in on our short but important body of knowledge survey and tell us what you think about the IASSC BoK’s.


1 It is not practical to survey and interview every organization and professional involved in Lean Six Sigma as to the content subject matters and methods that are used. In an effort to supply the Industry with a Lean Six Sigma Body of Knowledge that is representative and worthy of being adopted as a viable and practical minimum competency standard, IASSC has employed a variety of techniques to research, survey and garner feedback on the topics taught by various professionals and organizations. The IASSC Lean Six Sigma Body of Knowledge is a voluntarily adopted standard, which by various measures, has been widely accepted across the Industry. If you would like to provide your own input on the IASSC Body of Knowledge, please complete the IASSC BoK Survey and we welcome you to contact us.