Project Management guide · Project management fundamentals
Lean vs Six Sigma (and Lean Six Sigma) Explained
Lean and Six Sigma are both process improvement approaches, but they attack different problems. Lean removes waste to make work flow faster; Six Sigma reduces variation to make results more consistent. Lean Six Sigma combines them.
Key takeaways
- Lean removes waste; Six Sigma reduces variation.
- Lean Six Sigma combines both, usually through DMAIC.
- Choose based on whether the problem is speed or consistency.
Side by side
| Lean | Six Sigma | |
|---|---|---|
| Origin | Toyota Production System | Motorola, 1980s |
| Focus | Waste and flow | Variation and defects |
| Main method | Value stream mapping, kaizen | DMAIC |
| Typical tools | 5S, kanban, VSM, pull | Statistics, control charts, root-cause analysis |
| Results | Faster delivery, less waste | More consistent quality |
| Approach to data | Visual and practical | Statistical and rigorous |
Lean Six Sigma
Lean Six Sigma combines Lean's speed and waste reduction with Six Sigma's statistical rigour. Projects typically follow DMAIC while using Lean tools to remove waste. Certification uses the same belt structure as Six Sigma.
When to use which
- Lean: work is slow, with long queues, handoffs and waiting.
- Six Sigma: results are inconsistent or defect rates are high, and you have data to analyse.
- Lean Six Sigma: both problems exist, which is common.
Frequently asked questions
Which is better, Lean or Six Sigma?
Neither in general. Lean is better for speed and flow; Six Sigma for consistency and defects.
Is Lean Six Sigma worth learning for project managers?
It is valuable for project managers in operations, manufacturing, healthcare and process improvement roles.
What is the difference between Lean and Six Sigma?
Lean removes waste and improves flow; Six Sigma reduces variation and defects using statistics.
What is Lean Six Sigma?
A combination of Lean's focus on speed and waste with Six Sigma's statistical rigour, typically following DMAIC and using Lean tools.
Lean vs Six Sigma: when should I use Lean?
When work is slow, with long queues, handoffs and waiting, rather than inconsistent results.
Lean vs Six Sigma: when should I use Six Sigma?
When results are inconsistent or defect rates are high and you have data to analyse.
Where did Lean and Six Sigma come from?
Lean came from the Toyota Production System; Six Sigma was developed at Motorola in the 1980s.
Does Lean Six Sigma use belts?
Yes. It uses the same belt structure as Six Sigma: Yellow, Green, Black and Master Black Belt.
Which Lean tools are used in Lean Six Sigma?
5S, kanban, value stream mapping, pull systems and kaizen events.
Which Six Sigma tools are used in Lean Six Sigma?
Statistical tools such as control charts, hypothesis testing and regression, plus root-cause analysis. See Six Sigma.
Can Lean and Six Sigma be used with Agile?
Yes. Lean ideas underpin Kanban, and Six Sigma's data-driven root-cause analysis can support quality improvement in any approach.