Six Sigma is a comprehensive and flexible system for achieving, sustaining and maximizing business success. Six Sigma is uniquely driven by close understanding of customer needs, disciplined use of facts, data, and statistical analysis, and diligent attention to managing, improving, and reinventing business processes (from the book The Six Sigma Way by Pande, Neuman, and Cavanagh).
The Six Sigma methodology is based on the concept that process variation can be reduced using statistical tools so that a process centered at the target has six Standard Deviations (sigma) between the process mean (target) and the nearest specification limit, at which point (adjusting for a shift over time of 1.5 sigma) the process will produce only 3.4 Defects per million opportunities. Six Sigma projects are built on a DMAIC framework of five phases: Define, Measure, Analyze, Improve, Control. Practitioners are given a "Belt" title (Yellow Belt, Green Belt, Black Belt) that corresponds to their level of experience.
Lean is a set of tools developed to reduce the waste associated with the flow of materials and information in a process from beginning to end. The goal of Lean is to identify and eliminate non-essential and non-value added steps in the business process in order to streamline production, improve quality and gain customer loyalty.
Lean Methods can be employed within the DMAIC framework to augment Six Sigma tools when the project focus is to improve process speed and efficiency.
Lean Six Sigma (LSS) is an increasingly popular combined management approach that emphasizes use of Lean methodologies and tools to identify and remove waste and increase process velocity, followed by use of Six Sigma methodologies and tools to identify and reduce or remove process variation. Design For Six Sigma (DFSS), a variant of Six Sigma, is a methodology used to design from scratch or re-design a product or process to one that meets customer requirements and has an expected quality level of Six Sigma. DFSS is about “getting it right the first time” instead of improving later (the focus of DMAIC Six Sigma).
Design for Lean Six Sigma (DFLSS)? That's all the tools and techniques put together. A growing number of deployments are describing their efforts as DFLSS.
Many companies avoid the above terminology, preferring to refer to their systems as Process Improvement, Continuous Improvement, or Process Excellence, but the tools and techniques are the same. For more definitions, visit SigmaPedia.com, the Lean Six Sigma Free Online Encyclopedia of all things Six Sigma. |
The LSS methodology relies on an impressive number of tools and techniques, many of which (e.g., Fishbone Diagrams, Statistical Process Control Charts, 5S) have been co-opted from older quality methodologies. This makes LSS more familiar to many quality practitioners and so easier to learn. The DMAIC framework is used to organize the tools into the appropriate order for use in project work. 
