Also called DMAIC, black belt, green belt, Lean Six Sigma
What is Six Sigma?
A structured, statistical method for reducing variation, used on problems where nobody knows the cause.
What else it is called
- Other names
- DMAIC, black belt, green belt, Lean Six Sigma
- In French
- Six Sigma
Related entries
Understanding six Sigma
A method for attacking variation using measurement and statistics, developed at Motorola in the 1980s and spread widely by General Electric. Projects follow five phases: define the problem and what it costs, measure the current performance and confirm the measurement system is trustworthy, analyse the data to find the real drivers, improve by changing them, and control so the gain holds.
Its strength is problems where the cause is genuinely unknown and the data is noisy, which is exactly where opinion and five whys both fail. Its weakness is cost. A black belt project absorbs months and real training, and a great many plant problems have a visible cause that a few days of lean work would remove for nothing.
Most manufacturers who use both end up using lean for flow and waste, and Six Sigma for a small number of stubborn quality problems that have resisted everything else.
In practice
Before commissioning a project, ask whether anybody on the floor already knows the answer. If three people do, you have a management problem rather than a statistical one.
Frequently asked
What is Lean Six Sigma?
The two methods used together: lean tools for flow, waste and speed, and Six Sigma tools for variation and defects. Most training programmes now teach the combination, because the problems in a real plant do not sort themselves neatly into one camp.
Do we need belts to do this?
Not to get value from the measurement discipline. You do need someone with real statistical training for the analysis phase of a genuine Six Sigma project, otherwise the tools get used to confirm what somebody already believed.