Lean Six Sigma combines two methodologies into one framework: Lean (eliminating waste) and Six Sigma (reducing variation and defects). Together they give you a structured, repeatable way to solve process problems — DMAIC for improving existing processes, DMADV for designing new ones.
Lean Six Sigma isn't one technique — it's two methodologies merged into a single discipline. Understanding both halves is the key to using it well.
Lean originated in manufacturing (the Toyota Production System) and focuses on removing anything that doesn't add value for the customer. Lean identifies 8 types of waste: defects, overproduction, waiting, non-utilised talent, transportation, inventory, motion and extra processing (remembered as DOWNTIME).
Six Sigma is a statistical approach developed at Motorola, focused on reducing process variation until defects become extremely rare — the name refers to a target of 3.4 defects per million opportunities. It uses data and measurement to find and remove root causes of variation.
Combined, Lean Six Sigma gives you Lean's speed and waste-focus with Six Sigma's rigour and data discipline. Read our full explainer: What is Lean Six Sigma?
Which one you use depends on whether you're fixing an existing process or designing a new one.
Define, Measure, Analyse, Improve, Control. The most widely used methodology path — for fixing a process that already exists but isn't performing well.
Define, Measure, Analyse, Design, Verify. Used when there's no existing process to improve — you're building something new from scratch.
Less common for small businesses — most start with DMAIC on an existing process.
Lean Six Sigma uses a belt system (borrowed from martial arts) to signal how deeply someone understands and can apply the methodology.
Understand the methodology's core concepts and can support or lead a basic DMAIC project. Sufficient for most team members and small business owners.
Can independently lead DMAIC projects using statistical tools, run experiments and manage project teams. The typical level for an improvement champion.
Expert-level statistical methods, trains other belts, leads multiple concurrent projects and drives methodology adoption across an organisation.
Every phase of the methodology has a standard toolkit. Here's what's used where.
Lean Six Sigma isn't the only improvement methodology. Here's how it compares to the alternatives you'll encounter.
A precision engineering firm used the complete DMAIC methodology to cut defects on its highest-volume product line from 4.2% to 0.8% — following each phase in sequence: defining the problem with a project charter, measuring two weeks of baseline data, analysing with a Pareto chart, improving with a redesigned fixture, and controlling with ongoing chart monitoring.
An accountancy practice applied the same DMAIC structure to a service process — client email response times — proving the methodology works identically whether the "product" is a physical part or a service interaction.
See more real-world applications on our Lean Six Sigma for Small Businesses page.
It's a combined methodology that merges Lean's focus on eliminating waste with Six Sigma's focus on reducing process variation and defects. It uses structured frameworks — primarily DMAIC — to systematically improve processes using data.
Define, Measure, Analyse, Improve and Control. Each phase has specific tools and outputs, moving from defining the problem through to putting permanent controls in place so improvements last.
Both terms are used interchangeably in practice. It's a methodology in that it defines a philosophy and approach (reduce waste, reduce variation), and a framework in that it provides structured steps (DMAIC) and tools to follow.
Lean focuses on removing waste and speeding up flow. Six Sigma focuses on reducing variation and defects using statistical analysis. Lean Six Sigma combines both — using Lean's speed with Six Sigma's data rigour.
No — the methodology itself is open and can be self-taught using free resources. Certification (White through Black Belt) demonstrates proficiency and gives structured training, but you can start applying DMAIC today using free templates and calculators.
DMAIC (Define, Measure, Analyse, Improve, Control) improves an existing process. DMADV (Define, Measure, Analyse, Design, Verify) designs a new process or product from scratch. Most small businesses use DMAIC since they're improving existing operations.
Start with the free White Belt course and get a certificate covering the full Lean Six Sigma methodology.