Table 1.

Comparison of Six Sigma, Lean, and the Model for Improvement

Six Sigma	Lean	Model for Improvement
Improvement philosophy
Continuous improvement	Continuous improvement	Daily improvement
Reduce unwanted variability	Staff respect and empowerment	Small–scale rapid cycle change with iterative learning
Approach
Five-phased process (define, measure, analyze, improve, and control)	Differentiate value- from nonvalue-added activities (waste)	Set an aim
	Focus improvement efforts on eliminating waste	Create balanced measures
		Identify and test changes
Common tools
Mathematical modeling	Flow diagrams	Process mapping
PDSA cycles	Kaizen events	PDSA cycles
Control charts	Run charts	Run charts
	PDSA cycles	Control charts
Training
Experience with quantitative statistics	Lean apprenticeship	On the job improvement experience
On the job improvement experience	On the job improvement experience
Project length for improvement
Months	Weeks to months	Days to weeks
Limitations
Complex and less accessible to frontline staff	Japanese terms can lead to confusion	Diagnostic tools and change ideas are adapted from other frameworks
Not ideal for projects focused on improving flow/speed	Not ideal for projects focused on statistical control and reducing variation
Applications
Cause of variation is unknown	Problems that can be directly observed and managed visually	The main cause of the problem is already determined, and change ideas are easily identified
No immediate improvement solution exists	Increasing process flow and speed	Problems with established evidence–based solutions

PDSA, Plan-Do-Study-Act.