Comparison of Lean and Six Sigma

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.

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?