Comparison of Lean and Six Sigma

Comparison of principles

This table compares the principles of Lean with the principles of Six Sigma.

Methodology

Lean

Six Sigma

Theory
  • Reduce waste
  • Reduce variation
Application guidelines
  • Identify value
  • Identify value stream
  • Flow
  • Pull
  • Perfection
  • Define
  • Measure
  • Analyse
  • Improve
  • Control
Focus
  • Flow
  • Problem
Assumptions
  • Waste removal will improve performance
  • Many small improvements are better than systems analysis
  • A problem exists
  • Figures and numbers are valued
  • System output improves if variation in all processes is reduced
Primary effect
  • Reduced flow time
  • Uniform process output
Secondary effects
  • Less variation
  • Uniform output
  • Less inventory
  • New accounting system
  • Flow metrics
  • Improved quality
  • Less waste
  • Fast throughput
  • Less inventory
  • Variation metrics
  • Improved quality
Criticisms
  • Statistical or system analysis not valued
  • System interaction not considered
  • Processes improved independently

Comparison of toolsets

This table shows a comparison of the commonly used tools of Lean and Six Sigma.

Area

Lean

Six Sigma

Process mapping
  • Value Stream Mapping
  • SIPOC
  • Swim-lane diagrams
  • Detailed process maps
Voice of the customer
  • Interviews
  • Interviews
  • CTQ trees
Analysis
  • 5 Whys
  • Statistical Process Control
  • (SPC)
  • Takt time
  • Overall Equipment Efficiency
  • (OEE)
  • Statistical Process Control
  • (SPC)
  • Process capability
  • Applied statistics
  • Cause and Effect diagram
  • Pareto Charts
Process improvement
  • Process redesign
  • 5S
  • TPM
  • Visual controls
  • Process redesign

Similarities and differences

This table contrasts the commonly taught approaches to Lean and Six Sigma.

Lean

Six Sigma

Specify Value
What is important in the eyes of the customer?
Define
What is important?
Identify the Value Stream
What is the entire Value Stream?
Measure
How are we doing?
Flow
How will the material and information flow through our process?
Analyse
What is wrong?
Pull
How can we let the customer pull products, rather than pushing products?
Improve
What needs to be done?
Perfect
How can we optimise our processes?
Control
How do we sustain the improvements?
Comparing methodologies
Lean and Six Sigma are process-based improvement methodologies: both were developed in manufacturing environments, both have proven their effectiveness. Current emerging trends are indicating that integrating the best elements of both methodologies offers a better option.