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Lean Six Sigma terms in plain language
You do not need to be a specialist to follow the method. Here is what the vocabulary on this site actually means, in everyday words.
Improvement methods
- Lean
- A way of working that removes waste so work flows with less waiting, less rework and less effort.
- Six Sigma
- A data-driven approach that reduces variation, so a process produces the same good result every time.
- Lean Six Sigma
- Lean and Six Sigma together — remove the waste and reduce the variation at the same time.
- DMAIC
- The five-phase method for improving a process that already exists: Define, Measure, Analyse, Improve, Control.
- DMADV
- The five-phase method for designing something new: Define, Measure, Analyse, Design, Verify.
- Kaizen
- Japanese for "change for the better" — small, continuous improvements made by the people doing the work.
- PDSA
- A fast improvement cycle: plan a small change, do it, study what happened, then act — adopt it or adjust it.
- 5S
- Five steps that keep a workplace organised: Sort, Set in order, Shine, Standardise, Sustain.
- A3 problem solving
- A one-page story of a problem, its root cause, the countermeasures and the result — named after A3-sized paper.
- Value stream mapping
- Drawing the whole flow of a process from start to finish, so waiting, rework and delays become obvious.
- Gemba walk
- Going to where the work actually happens to see the process first-hand, rather than reading about it.
- Kanban
- A visual board that limits how much work is in progress, so the team finishes work instead of starting more.
- Standard work
- Writing down the current best way to do a task, so everybody performs it the same way.
- Poka-yoke
- Mistake-proofing: a design step that makes an error impossible or immediately obvious.
Analysis tools
- Root cause analysis
- Finding the underlying reason a problem happens, rather than repeatedly fixing the symptom.
- 5 Whys
- Asking "why?" again and again — usually about five times — to travel from a symptom to its root cause.
- Fishbone diagram
- A fish-shaped diagram that sorts possible causes into categories such as people, machine, method, material, measurement and environment.
- Pareto chart
- A bar chart that shows which few causes account for most of the problems, so you fix the biggest ones first.
- FMEA
- A structured review of what could fail, how badly it would hurt and how likely it is, so you act on the worst risks first.
- SIPOC
- A one-page view of a process: Suppliers, Inputs, Process, Outputs, Customers.
- Control chart
- A run chart with control limits that shows whether a process is stable, or whether something real has changed.
- Gage R&R
- A check that the measurement system itself can be trusted before you act on its numbers.
- Spaghetti diagram
- A map of how far people or parts travel through a workspace, used to cut wasted movement.
Measures and metrics
- Voice of the customer
- What customers say they need, collected directly from them rather than assumed.
- Critical to quality
- The few things customers genuinely care about, turned into something you can measure.
- Baseline
- The measured "before" number you compare your improvement against.
- Cycle time and lead time
- Cycle time is how long one item takes to work on; lead time is how long the customer waits from request to delivery.
- Takt time
- The pace you need to produce at to match customer demand: available working time divided by units needed.
- Cpk
- A number showing how comfortably a process fits inside the customer's limits — higher is better, and 1.33 is a common target.
- DPMO
- How many defects you would see in a million chances, used to express a Sigma level.
- First pass yield
- The share of work completed correctly the first time, with no rework.
- OEE
- How much of the time equipment is available, running at its proper speed and producing good output.
Belt levels
- White Belt
- An introduction to Lean Six Sigma ideas and vocabulary.
- Yellow Belt
- Team members who support improvement work and use the basic tools.
- Green Belt
- Practitioners who lead smaller improvement projects alongside their day job.
- Black Belt
- Full-time improvement leaders who run complex projects and coach Green Belts.
- Master Black Belt
- The most experienced level — sets improvement strategy, trains Belts and governs the project portfolio.