3
Methodologies Compared
Speed
Lean's Focus
Quality
Six Sigma's Focus
Both
Lean Six Sigma

The Quick Comparison

Lean and Six Sigma attack different problems. Lean eliminates waste to improve speed and flow. Six Sigma reduces variation to improve quality and consistency. Lean Six Sigma combines both.

DimensionLeanSix SigmaLean Six Sigma
FocusEliminate wasteReduce variationBoth
OriginToyota (1950s)Motorola (1986)2000s merger
Tools5S, VSM, KanbanDMAIC, SPC, DOEAll of the above
SpeedFast — days to weeksSlower — weeks to monthsFlexible
Data needsObservation-basedData-intensiveBalanced
Best forFlow, throughput, lead timeDefects, consistency, yieldComplex operations

When to Use Each

🏭 Use Lean When...

  • Processes have obvious waste (waiting, motion, overproduction)
  • Lead times are too long
  • Inventory is piling up
  • You need quick wins to build momentum

📊 Use Six Sigma When...

  • Defect rates are high and the root cause is unclear
  • Process variation is out of control
  • You need statistical proof before making changes
  • The problem is complex with many possible causes
🎯 Use Lean Six Sigma when you need both Most real-world operations have waste AND variation. Lean Six Sigma lets you use 5S to organize the workspace (lean), then DMAIC to attack a chronic defect (six sigma), all within the same improvement program.

A Practical Decision Framework

🤔 Which Should I Use? Decision Guide

Can you see the problem by walking the floor? → Start with Lean. Do a gemba walk, identify waste, fix it fast.

Is the problem intermittent and hard to pin down? → Use Six Sigma. Collect data, run analysis, find the hidden root cause.

Is the problem "everything is slow AND unreliable"? → Lean Six Sigma. Use lean to speed up flow, then six sigma to lock in quality.

💡
Don't overthink the methodology In practice, the best teams don't label their work as "lean" or "six sigma." They just use whatever tools solve the problem at hand. The methodology is a guide, not a religion.

Interactive Demo

Classify manufacturing problems as Lean or Six Sigma. See which tools apply from each methodology.

⚡
Try It Yourself
Lean vs Six Sigma Selector
▼
For each problem scenario, decide: Is this a Lean problem (waste/flow), a Six Sigma problem (variation/defects), or both? See which tools apply and why.
Scenario #1: Excessive Work-in-Process Inventory
Your production floor has 3 weeks of WIP sitting between stations. Lead time is 15 days but actual processing time is only 2 days. Customers are complaining about long delivery times.
What type of problem is this?
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Take this to a room

The running order

For a team choosing an approach. They should leave able to pick between lean and Six Sigma for a specific problem.

7 beats · 8 min
  1. 1

    Two different questions

    Lean asks why is this taking so long. Six Sigma asks why is this inconsistent.

    • Lean attacks waste and flow. Speed is its focus.
    • Six Sigma attacks variation and defects. Quality is its focus.
    • Neither is a superset of the other.

    Ask the room Which of those two questions describes our biggest problem?

  2. 2

    They come from different places

    Knowing the origin explains the difference in style.

    • Lean grew on a shop floor, from Toyota, through observation.
    • Six Sigma grew at Motorola, from statistics, through measurement.
    • One is a way of seeing. The other is a way of proving.
  3. 3

    When lean is the right tool

    Three signals that the answer is flow rather than statistics.

    • Long lead times with short processing times.
    • Piles of WIP between steps.
    • Obvious waste - walking, searching, waiting - that nobody needs a study to see.
  4. 4

    When Six Sigma is the right tool

    Three signals that the answer is variation rather than flow.

    • A defect rate that nobody can explain.
    • Output that varies between shifts, operators or lots without an obvious cause.
    • A problem that has survived several confident fixes.

    Ask the room Which of our problems has survived multiple fixes?

  5. 5

    Lean Six Sigma is the combination, not a compromise

    Use the DMAIC structure and populate it with lean tools where they fit.

    • Define and measure benefit from lean's go-and-see discipline.
    • Analyse benefits from the statistical toolkit.
    • Improve and control take from both.
  6. 6

    The decision framework

    One question, asked before choosing.

    • Do we know what causes the problem?
    • If yes, and the problem is delay - lean.
    • If no, and the problem is variation - Six Sigma.
    • If the problem is obvious, neither. Just fix it.
  7. 7

    Do not let the belt decide the tool

    The most common failure is applying whichever method the available person was trained in.

    • A trained black belt will find a statistical problem.
    • A lean practitioner will find flow waste.
    • Diagnose first, then choose the person.

    Ask the room Which method do we default to here, and why?

Related Guides

🏭 Lean Manufacturing
The foundation: waste elimination
📊 Six Sigma
DMAIC and defect reduction
📈 Kaizen
Daily continuous improvement