The third component and first “S” in L.E.S.S. stands for Six Sigma. The focus and principles behind Six Sigma is the basis for it in the L.E.S.S. approach—Continuous Improvement (CI). Six Sigma is just one type of continuous improvement methodology. Another common CI methodology would be the PDCA (Plan, Do, Check, Act) cycle. CI is used to always look to improve the quality of processes, products and services for the organization and their customers. One of the largest problems that impede consistent high levels of quality is from process variation. To improve quality, the many variations must be identified, analyzed, measured, improved and controlled in a systematic way to ensure the process inputs result in the highest quality level of output that meets customer requirements. Specifically to Six Sigma the level of performance for each process should equal no more than 3.4 defects per million.
Including Six Sigma into the L.E.S.S. approach is invaluable for two reasons: 1) It provides a common language, concepts and methods to continuous improvement and 2) The methodology allows one to drill down to the factors causing variation. This is something the PDCA and A3 thinking of Lean cannot do.