The International Standard for
Optimized Lean Six Sigma
LSSx.0 provides the knowledge, practical capabilities, and thinking needed to identify operational problems and select the most effective improvement trajectory — achieving faster resolution and sustainable results.
How problems are classified
Match capabilities to problem complexity
MBB
MBB
BB
BB
YB
YB
GB
4
3
Sigma
3
4
5
Problem category
Yellow Belt
Green Belt
Black Belt
Master Black Belt
Overview
The LSSx.0 methodology, developed by Youri Buffe, builds upon the traditional Lean Six Sigma framework to provide a more structured approach to improvement projects.
Based on an original typology of statistical problems, the methodology adapts the problem-solving approach to the nature and complexity of the issue being addressed.
This framework helps practitioners select the most appropriate analytical tools and follow the most efficient path toward sustainable solutions.
LSSx.0 Framework
The LSSx.0 Framework aligns competency levels with problem typology, complexity and expected process performance.
Competency Level
Problem Types Addressed
Performance Level
Lean Practitioner
Flow problems
Rapid & efficient processes
Yellow Belt
Flow + Simple (discernible) quality problems
Standard performance (< 3σ)
Green Belt
Flow + Simple (discernible) + Complex (non-discernible) quality problems
Standard performance (< 3σ)
Black Belt
Flow + Simple (discernible) + Complex (non-discernible) quality problems
Advanced performance (3–4σ)
Master Black Belt
Flow + Simple (discernible) + Complex (non-discernible) quality problems
World-class performance (> 4σ) + Organizational deployment capability
Note: Quality is understood in its broad sense as the ability to consistently meet customer and stakeholder requirements.
The LSSx.0 Body of Knowledge
The LSSx.0 standard is formally defined and documented through three reference books, which together constitute its Body of Knowledge.
LSSx.0 – 1
Flow Problems and Lean Management
Flow problems
LSSx.0 – 2
Discernible Problems and Methodological Foundation
Simple (discernible) quality problems
LSSx.0 – 3
LSSx.0 – 3
The Statoscope: Resolving Indiscernible and Related Statistical Problems
Complex (non-discernible) quality problems
Governance
01
The LSSx.0 standard is maintained by Lean Six Sigma International to ensure a consistent and up-to-date framework for Lean Six Sigma competencies and certification.
02
The standard and its Body of Knowledge are regularly reviewed and updated to reflect evolving professional practices and methodologies.
03
LSSx.0 defines the knowledge and practical capabilities expected at each certification level, from Yellow Belt to Master Black Belt.