How do Lean and Six Sigma differ?
- Aim: lean shortens the path from request to delivery. Six Sigma makes the result the same every time.
- Origin: lean comes from the Toyota Production System. Six Sigma came from Motorola in the 1980s.
- Evidence: lean works from walking the process, time and queue observations and value stream mapping. Six Sigma needs measured results over many cycles.
- Method: lean uses many small changes, such as 5S and kaizen. Six Sigma uses structured DMAIC projects.
- People: lean is for every team member. Six Sigma projects are led by trained belts.
When should you use each one?
Use lean when the work is slow, queues build up, people repeat steps or handoffs add delay. Use Six Sigma when the output varies, defects keep returning and the cause is not obvious. When both are true, start with lean, then measure what is left. A calmer, simpler process is easier to measure and easier to improve.
Can you use them together?
Yes, and most organisations do, because real problems are rarely only slow or only variable. A site might remove a queue with lean, then use a short measured project to deal with the defects that remain. The combined approach is called Lean Six Sigma, sometimes written Lean e 6 Sigma. See Six Sigma tools for the tools used in each DMAIC phase.