Glossary
The vocabulary of Lean Six Sigma
Lean Six Sigma is practised in English, taught in every language, with Japanese words in the middle. The result: three people around the same table use the same word for three different things. This glossary pins the terms down.
Each entry gives the term, its French equivalent, and — where one exists — the standard that holds the reference definition. That is a pointer, nothing more: the definitions below are written from scratch and make no claim to restate a normative text. When the stakes are contractual, the standard prevails, not us.
Each entry also has a section called the common mistake. It is the part you will not find in a textbook: what I keep seeing on the shop floor, written in the first person because it commits nobody but me. I am Clément Rat, Lean Six Sigma Black Belt, and I write these pages myself — who is behind beltup.
68 terms published, 68 reviewed in English — the others open in French, and the entry says so.
Method
DMAIC · DMAIC
DMAIC is the five-phase problem-solving approach — Define, Measure, Analyze, Improve, Control — that structures every Six Sigma project.
Continuous improvement · Kaizen (amélioration continue)
Kaizen is continuous improvement in small steps, led by those who do the work, as opposed to breakthroughs driven from outside.
Short Interval Management · AIC (animation à intervalle court)
Short interval management is a system of short, frequent team huddles, organised in cascade, where each level handles what it can and escalates the rest within the day.
Lean house (TPS house) · Maison du Lean
The Lean house represents the Toyota Production System as a building: a foundation of stability, two pillars — just-in-time and jidoka — and a roof that carries the objectives.
SIPOC · SIPOC
A SIPOC describes a process on one page in five columns — suppliers, inputs, process, outputs, customers — to agree on its scope before analysing it.
Gemba / genchi genbutsu · Gemba (le terrain)
The gemba is the place where the work is actually done, and the gemba walk is the practice of going there to observe the process rather than reading the report about it.
PDCA / Plan-Do-Check-Act · PDCA (roue de Deming)
PDCA is the four-step improvement cycle — plan, do, check, act — whose value lies in its last two steps, almost always skipped.
Lean fundamentals · Fondamentaux du Lean
Lean seeks to give the customer what they value while consuming as few resources as possible. Five principles organise the approach: define value, map the flow, make it continuous, pull it by demand, aim for perfection.
DFSS — design for Six Sigma · DFSS — conception pour Six Sigma
DFSS applies the Six Sigma logic to design, when there is no process yet to improve. It aims to create a product or service that is robust from the outset, rather than correcting afterwards.
Business process management · Gestion des processus
Managing by processes means organising steering around what crosses the company to produce a service for the customer, rather than around the departments that make it up.
Hoshin Kanri — policy deployment · Hoshin Kanri (déploiement de la stratégie)
Hoshin Kanri translates a few strategic orientations into objectives and actions at every level of the organisation, through a top-down and bottom-up negotiation rather than a cascade of orders.
Project selection · Sélection de projets
Choosing which improvement projects to launch is the decision that determines the return of a Lean Six Sigma approach — far more than the mastery of the tools used afterwards.
Team management · Management d’équipe
Leading an improvement team means obtaining the cooperation of people who do not report to you, on a subject they did not choose, on top of their work.
Change management · Conduite du changement
A demonstrated improvement is not an adopted improvement. Change management deals with the gap between the two, which is the most frequent cause of failure of Lean Six Sigma projects.
RACI matrix · RACI — matrice des responsabilités
RACI is a table that assigns, for each activity, four distinct roles: who does the work, who answers for the result, who is consulted before, who is informed after.
Voice of the customer · Voix du client (VOC)
The voice of the customer is the set of expectations expressed by those the process serves, collected in their words before being translated into measurable characteristics.
Project sponsor (champion) · Sponsor de projet (champion)
The sponsor is the manager who carries an improvement project at the level where trade-offs are made: they open doors, decide priorities and answer for the result to senior management.
Five Lean principles · Les cinq principes du Lean
The five Lean principles form the framework of a transformation: they say where to take hold of it and in what order to proceed, each step making the next one achievable.
Quality function deployment (QFD) · QFD — déploiement de la fonction qualité
QFD is a matrix that links customer expectations to the technical characteristics of the product, weighting each link to bring out the characteristics on which design must focus its effort.
Control plan · Plan de contrôle (plan de surveillance)
The control plan writes down what is monitored on a process, how, how often, by whom, and what is done when the measurement leaves the expected range.
Lean tools
Value Stream Mapping · Cartographie de la chaîne de valeur (VSM)
A VSM shows on a single sheet the physical flow and the information flow of a product, from order to delivery, to make visible the time when nothing happens.
5S · 5S
5S organises the workstation in five steps — sort, set in order, shine, standardize, sustain — so that an anomaly is visible at once.
Single Minute Exchange of Die · SMED (changement rapide d’outil)
SMED cuts changeover time by separating what can be prepared while the machine runs from what requires it to stop, then converting the second into the first.
Seven wastes · Les sept gaspillages (muda)
The seven wastes classify everything a process consumes without the customer having asked for it: overproduction, waiting, transport, over-processing, inventory, motion and defects.
Kanban · Kanban
A kanban is a signal — card, bin or empty location — that authorises production or replenishment, and that puts the flow in pull rather than push.
Yamazumi chart · Yamazumi (diagramme d’équilibrage)
The Yamazumi chart stacks the work content of each station into bars and compares it with the takt time, to see at a glance who is overloaded and who has spare capacity.
Poka-yoke / mistake-proofing · Poka-yoke (détrompeur)
A poka-yoke is a device that makes the error impossible, or that flags it the instant it occurs, before it becomes a defect.
Jidoka / autonomation · Jidoka (autonomation)
Jidoka gives the machine — and the operator — the power to stop production as soon as an anomaly appears, so that the defect is treated instead of being passed on.
Heijunka / production levelling · Heijunka (lissage de la production)
Heijunka spreads volume and variety evenly over the period, instead of producing orders in their order of arrival with the peaks and troughs that entails.
Visual management · Management visuel
Visual management makes the state of a process readable without having to ask: anyone entering the area must see within a few seconds whether the situation is normal, and if not, where it is not.
Flow (one-piece, push, pull) · Flux (pièce à pièce, poussé, tiré)
Flow describes the way work moves from one step to the next. Lean seeks to make it continuous and to trigger it by real demand rather than by forecasts.
TPM — total productive maintenance · TPM — maintenance productive totale
TPM aims at equipment availability by involving the operators in its upkeep, rather than reserving maintenance for a dedicated department that steps in after the breakdown.
Standardized work · Travail standardisé
Standardised work is the best sequence known to date for carrying out a task, written by those who do it, and meant to be improved as soon as something better is found.
ECRS — eliminate, combine, rearrange, simplify · ECRS — éliminer, combiner, réorganiser, simplifier
ECRS is a grid of questions applied to each operation of a process, in an order that is not negotiable: can it be removed, grouped, moved, or made simpler?
Process flow analysis · Analyse de déroulement
Process flow analysis records, in order, every step a product or a file goes through, classifying it by nature — operation, transport, inspection, delay, storage — to bring out what contributes nothing.
Value added · Valeur ajoutée
A value-added activity is one the customer would agree to pay for if it were described to them. Everything else splits between what is necessary without being wanted, and what can disappear.
Work in progress (WIP) · En-cours (WIP)
Work in progress is everything that has entered a process without yet having left it: started parts, open files, unclosed tickets. It is the quantity that is easiest to count and most rarely steered.
Andon · Andon
The andon is the device that makes an anomaly visible the instant it occurs, and calls for help. It is not a warning light: it is an alert chain whose value lies in the response time.
Muri and mura · Muri et mura — surcharge et irrégularité
Muri is the overburden imposed on people and equipment; mura is the unevenness of the load over time. They are the two causes that produce the waste one is about to fight.
Autonomous maintenance (jishu hozen) · Maintenance autonome
Autonomous maintenance entrusts routine upkeep — cleaning, inspection, lubrication, retightening — to those who run the equipment, so that degradation is detected before the breakdown.
Spaghetti diagram · Diagramme spaghetti
The spaghetti diagram traces on a floor plan the actual movements of a person, a document or a part. The tangle obtained makes visible a distance nobody was counting.
Problem solving
Ishikawa / fishbone diagram · Diagramme d’Ishikawa (5M)
The Ishikawa diagram lays out in a fishbone all the possible causes of a problem, grouped by family, so as not to stop at the first plausible hypothesis.
Pareto chart · Diagramme de Pareto
The Pareto chart ranks causes in decreasing order of importance and overlays their cumulative total, to identify the small number of them that produce most of the effect.
FMEA — Failure Mode and Effects Analysis · AMDEC
FMEA methodically lists the possible failure modes of a product or a process, assesses their severity, frequency and detectability, and prioritises the actions to take before the failure occurs.
Problem solving · Résolution de problèmes
Solving a problem, in the Lean Six Sigma sense, means going back from an observed symptom to a demonstrated cause, then checking that the action taken has indeed removed it — in that order, and without skipping a step.
Five whys · Les cinq pourquoi
The five whys consist of going back from an observed problem to a cause one can act on, by asking at each step why the previous step occurred.
A3 problem solving · Méthode A3
The A3 method holds a complete line of reasoning — background, current situation, causes, countermeasures, plan, follow-up — on a single A3-size sheet, whose space constraint is the main tool.
Measurement and indicators
Overall Equipment Effectiveness (OEE) · TRS (taux de rendement synthétique)
OEE measures the share of required time actually turned into good parts at nominal rate, as the product of three rates: availability, performance and quality.
Takt time · Takt time (temps takt)
Takt time is the pace set by customer demand: the available time divided by the quantity to deliver over the same period.
Process performance indicators · Indicateurs de performance du processus (IPP)
Performance indicators measure a process from a few complementary angles — quality, lead time, cost — distinguishing those that record a result from those that announce a drift.
MSA — measurement system analysis · MSA — analyse du système de mesure
Measurement system analysis checks that the instrument and the method are reliable enough for the data to be used to decide. Without it, every analysis rests on figures whose quality is unknown.
Quality metrics · Indicateurs qualité
Scrap rate, rework rate, first-pass yield, cost of poor quality: quality metrics put a figure on what defects cost, and above all on where they occur.
Lead time · Lead time (délai de traversée)
Lead time is the time between the customer’s request and its fulfilment, waits included. It is the delay the customer feels, and it almost never bears any relation to the sum of the working times.
Critical to quality (CTQ) · CTQ — caractéristique critique pour la qualité
A CTQ is the translation of a customer expectation into a measurable characteristic, with a target and limits beyond which the customer declares themselves dissatisfied.
Cycle time · Temps de cycle
Cycle time is the duration between two successive outputs of the same station or the same process. It describes a rate, is recorded with a stopwatch, and is never summed up by its mean.
MTBF and MTTR · MTBF et MTTR
MTBF is the mean time between two failures, MTTR the mean time to restore service. The first measures reliability, the second the ability to repair — and confusing them leads to treating the wrong problem.
Statistics
Process capability · Capabilité (Cp, Cpk, Pp, Ppk)
Capability indices compare the spread of a process with the tolerance interval: Cp measures what the process would be capable of if it were centred, Cpk what it is capable of as it stands.
DPMO / sigma level · DPMO et niveau sigma
DPMO expresses the number of defects per million opportunities to make one — a basis that puts a simple product and a complex product on the same scale, and that converts into a sigma level.
Descriptive statistics · Statistiques descriptives
Descriptive statistics summarise a data set with a few numbers: where it sits, how much it spreads, and what shape it has. It is the step that precedes any analysis, and the one most often skipped.
SPC — statistical process control · MSP — maîtrise statistique des procédés
Statistical process control tracks a process over time by means of control charts, so as to distinguish its normal variability from the events that warrant intervention.
Hypothesis testing · Tests d'hypothèse
A hypothesis test answers a single question: is the observed gap between two situations larger than what sampling chance produces on its own?
Regression analysis · Régression
Regression models the link between a quantity one wants to explain and one or more quantities that influence it. It quantifies what the scatter plot lets one guess.
DOE — design of experiments · Plans d'expériences
A design of experiments organises the trials to measure the effect of several factors at once, and detect their interactions, with far fewer trials than the intuitive method.
Correlation · Corrélation
Correlation measures the strength of the link between two quantities that vary together. It is summarised by a coefficient between −1 and 1, and is never read without the scatter plot it was drawn from.
ANOVA (analysis of variance) · ANOVA — analyse de la variance
Analysis of variance compares the means of several groups at once, judging whether the gap between the groups is large compared with the spread observed within each of them.
Histogram · Histogramme
The histogram shows the distribution of a measured quantity by grouping the values into classes. Its shape tells you about the process well before the calculation of a mean does.
Sampling · Échantillonnage
Sampling consists of measuring a part to conclude about the whole. Its validity depends on the way the units are drawn, far more than on their number.
Common cause and special cause variation · Causes communes et causes spéciales
All variation belongs to one of two families: the one the system produces permanently, and the one an identifiable event caused. Getting the family wrong leads to acting exactly at the wrong time.