The term Six Sigma comes from the Greek letter ‘σ’ that is used as the symbol for standard deviation. Six Sigma refers to how many standard deviations fall within the output of a process.
Simply put, Six Sigma means that there are fewer than 3.4 defects per million opportunities.
Many people know that the term Six Sigma was originally used at Motorola (in 1989), but few people realize that the term was trademarked (application filed in 1991) as well.
Six Sigma uses a data driven approach to solve major problems. In general, the tools Six Sigma uses are beyond the ability of most lay people. There is a lot of statistical analysis in Six Sigma. For that reason, many companies invest in creating Six Sigma black belts who help teams use the Six Sigma tools.
Because of Six Sigma’s need for specialized support, Lean is often chosen over Motorola’s brainchild. Lean is more accessible to a greater number of people in the organization, and is far simpler to learn the basic tools.
There is a great deal of overlap between Lean and Six Sigma—so much so that a new term, Lean Six Sigma, has developed. But in truth, it is not actually necessary to label your continuous improvement efforts. Just make sure that you create a culture that promotes improvement and use whatever tools work to make gains.