Published 22 February 2026 · 6 min read
Lean removes waste to improve speed and flow; Six Sigma reduces variation to improve consistency and quality. Most real-world processes have both problems, which is why most modern certification programs (including SigmaCS's) teach the combined Lean Six Sigma methodology by default.
Two different questions
Lean asks: 'where is time or effort being wasted in this process?' Its answer is the eight wastes (DOWNTIME) and tools like value stream mapping, 5S and kanban to remove them.
Six Sigma asks: 'why does this process produce inconsistent or defective output?' Its answer is DMAIC and statistical tools, hypothesis testing, process capability, control charts, to find and eliminate the root cause of variation.
Why most programs combine them
In practice, a slow process and a defect-prone process are often the same process. A hospital discharge that takes too long is also the one most likely to have documentation errors. That overlap is why Lean Six Sigma, Lean's flow tools plus Six Sigma's statistical rigor, has become the default curriculum at most training providers, including ours.
| Lean | Six Sigma | Lean Six Sigma | |
|---|---|---|---|
| Primary focus | Waste & speed | Variation & defects | Both |
| Core tools | Value stream mapping, 5S, kanban | DMAIC, hypothesis testing, SPC | DMAIC + Lean tools combined |
| Best fit | High-volume, low-complexity flow problems | Stable processes with quality/consistency issues | Most real-world operations |
| Certification at SigmaCS | Included within Lean Six Sigma track | Available as a standalone track | Available at every belt level |
Frequently asked questions
Do I need to learn Lean and Six Sigma separately?
No, our Lean Six Sigma courses teach both together at every belt level, so you don't need to complete two separate certification tracks to get both toolsets.
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