DMAIC
The five-phase improvement method: Define, Measure, Analyze, Improve, and Control.
Lean Six Sigma Body of Knowledge
This Body of Knowledge is a learning path through Lean Six Sigma as we teach it on this site: the DMAIC method, the Yellow, Green, and Black Belt roles, and the Lean tools you will meet on the job and on IASSC or ASQ exams. The goal is that you can start here and stay on our pages, instead of being sent out to a different website for each topic.
This is an independent study guide. It is not the official Body of Knowledge of IASSC or ASQ, and it is not a substitute for their exam handbooks. When you need official exam rules, scoring, or the current published BoK, use the certifying body. We link those official pages as references and keep the teaching on this site.
How to use this hub
Work from top to bottom if you are new. If you already have a project, jump to the tool you need, then use Previous and Next on each page to stay on the path. Pages marked “Guide ready” are ones you can study on this site today. Pages marked “Coming next” are planned on purpose — those are often the topics this site used to cover with an external link, and we will replace that link only after our own page is live and complete.
Foundations
Belt roles and responsibilities
What Yellow, Green, and Black Belts, Champions, and process owners typically own on a project.
Y G B Guide readyWhat is Six Sigma?
A short definition of the approach and why variation and defects matter.
Y G B Live — scheduled for a fuller rewriteHistory of Six Sigma and continuous improvement
Where the method came from and how it connects to earlier quality work.
Y G B Guide readyHow to get Six Sigma certified
Independent overview of IASSC, ASQ, and other exam paths. Official exam rules stay on the certifier’s site.
Y G B Guide readyDesign for Six Sigma (DFSS)
When you need to design or redesign a product or process rather than improve an existing one.
G B Guide readyLean foundation (learn these early)
These tools help you see flow and waste before you dive into formal statistics. They are taught in most Yellow Belt courses and used on almost every Green Belt project.
The 8 wastes (TIMWOODS)
Transportation, Inventory, Motion, Waiting, Overproduction, Overprocessing, Defects, and Skills — and how to spot them on a walk.
Y G B Guide ready5S
Sort, Set in Order, Shine, Standardize, and Sustain: a workplace system that makes normal work visible.
Y G B Guide readySIPOC diagrams
A one-page high-level map of Suppliers, Inputs, Process, Outputs, and Customers, usually built in Define.
Y G B Guide readyValue stream mapping
A map of material and information flow, with inventory, cycle time, and a lead-time timeline.
Y G B Guide readyKaizen and Kaizen Blitz
Continuous improvement as daily practice, and focused events that run a PDCA cycle quickly.
Y G B Guide readyPoka-yoke (mistake-proofing)
Devices and methods that prevent an error or make it obvious at the source, before it becomes a defect.
Y G B Guide readyKanban
A pull signal that limits work in process and tells an upstream step when to produce or move work.
Y G B Live — expansion plannedJust-in-time (JIT)
Producing and moving what is needed, when it is needed, in the amount needed.
G B Live — expansion plannedTotal productive maintenance (TPM)
Keeping equipment capable through planned maintenance and operator care.
G B Live — expansion plannedDefine
Voice of the customer (VOC)
How customer statements, complaints, and data are gathered and turned into requirements.
Y G B Live — expansion plannedCritical to quality (CTQ)
The measurable product or process characteristics that have to be met to satisfy the VOC.
Y G B Live — expansion plannedProject charter
Scope, business case, goals, team, and boundaries for a DMAIC project.
Y G B Live — expansion plannedKano model
A way to sort customer requirements into basic, performance, and delight features.
G B Live — expansion plannedQuality function deployment (QFD)
A structured way to carry customer needs into design and process requirements.
B Live — expansion plannedMeasure
Basic Lean Six Sigma metrics
Lead time, cycle time, WIP, yield, and other measures used on improvement projects.
Y G B Guide readyCheck sheet
A simple, structured form for collecting data at the place the work happens.
Y G Guide readyHistogram
A distribution of a measured characteristic, used to see shape, spread, and centering.
Y G B Guide readyWork in progress (WIP)
The inventory of unfinished work in the system, and why it drives lead time.
Y G B Guide readyCommon and special cause variation
The two kinds of variation that control charts are built to distinguish.
Y G B Guide readyProcess capability (Cp, Cpk, Pp, Ppk)
How a stable process compares to its specification limits, and when each index is the right one to quote.
G B Coming next — several external guides still point off-siteMeasurement system analysis (MSA / Gage R&R)
Whether your measurement system is capable enough for the decision you want to make.
G B Coming next — a frequent off-site link from the training guidesAnalyze
Pareto analysis and Pareto chart
Ranked categories with a cumulative line, used to focus on the vital few.
Y G B Guide readyIshikawa (fishbone) diagram
A structured cause-and-effect picture of possible drivers of a problem.
Y G B Guide ready5 Whys
A simple questioning method for walking from a symptom toward a root cause.
Y G Guide readyRoot cause analysis
A broader look at finding and confirming causes, including when 5 Whys is not enough.
Y G B Guide readyChoosing the right parametric test
A starting point for matching a hypothesis test to your data and question.
G B Live — a fuller hypothesis-testing guide is plannedHypothesis tests and nonparametric alternatives
t-tests, z-tests, ANOVA, proportions, and common nonparametric options, with a decision tree.
G B Coming next — this is the largest remaining cluster of off-site study linksDesign of experiments (DOE)
Planned experiments that estimate factor effects and interactions, including factorial designs.
B Coming nextImprove
Failure mode and effects analysis (FMEA)
A structured look at how a process or design can fail, and how to prioritize actions.
G B Guide readyPoka-yoke
Mistake-proof the Improve action so the error cannot easily return.
Y G B Guide readyKaizen events
Turn a cause into a small, tested change, then standardize what works.
Y G B Guide ready5S in Improve
Often the first physical change on the floor when motion, mixed materials, or hidden problems dominate.
Y G B Guide readyControl
Statistical process control charts
How control charts detect signals of special cause against a background of common cause.
Y G B Guide readyChoosing the right control chart
A guide to matching chart type to the kind of data you have.
G B Guide readyControl plan
The document that states what to measure, who reacts, and how the gain is held.
G B Live — expansion plannedIn-control process
What it means for a process to be statistically stable.
G B Guide readyBelt paths
Yellow Belt. Learn DMAIC, the eight wastes, 5S, SIPOC, VOC and CTQ at a basic level, Pareto, fishbone, 5 Whys, and what a control chart is for. Then take a Yellow Belt practice exam.
Green Belt. Add value stream mapping, capability (once that guide is on this site), measurement thinking, hypothesis tests, FMEA, Kanban and poka-yoke, and a real project charter. Practice with the IASSC Green Belt and ASQ Green Belt question sets.
Black Belt. Add DOE, QFD, more advanced statistics, DFSS, and enterprise deployment topics. Use the IASSC Black Belt and ASQ Black Belt practice exams, and the ASQ free training guide as a map of exam sections — then read the matching guides here.
Practice exams and tables
When you are ready to test yourself, start at the practice exams hub. Statistical tables used in many of those items live at Six Sigma tables (z, t, chi-square, F, and Poisson).
Frequently asked questions
Is this the official IASSC or ASQ Body of Knowledge?
No. It is our learning path, written so a visitor can study on this site. Official exam content, eligibility, and the current published Body of Knowledge remain with IASSC and ASQ. Use their sites for those facts.
Where should a complete beginner start?
Read the DMAIC overview, then the eight wastes, 5S, and SIPOC, in that order. After that, value stream mapping and Kaizen will make more sense, and you can follow Define–Measure–Analyze–Improve–Control through the tools above.