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Quality Glossary
ABSCISSA - The horizontal axis of a graph.
ACCEPTANCE REGION ALPHA RISK - The region of values for which the null hypothesis is accepted.
ALPHA RISK - The probability of accepting the alternate hypothesis when, in reality, the null hypothesis is true.
ALTERNATE HYPOTHESIS - A tentative explanation which indicates that an event does not follow a chance distribution; a contrast to the null hypothesis.
ANDON BOARD - A visual control device in a production area, typically a lighted overhead display, giving the current status of the production system and alerting team members to emerging problems.
ASSIGNABLE CAUSE - A source of variation which is non-random; a change in the source (”VITAL FEW” variables) will produce a significant change of some magnitude in the response (dependent variable), e.g., a correlation exists; the change may be doe to an intermittent in-phase effect or a constant cause system which may or may not be highly predictable; an assignable cause is often signaled by an excessive number of data points outside a control limit and/or a non-random pattern within the control limits; an unnatural source of variation; most often economical to eliminate.
ASSIGNABLE VARIATIONS - Variations in data which can be attributed to specific causes.
ATTRIBUTE - A characteristic that may take on only one value, e.g. 0 or 1.
ATTRIBUTE DATA - Numerical information at the nominal level; subdivision is not conceptually meaningful; data which represents the frequency of occurrence within some discrete category, e.g., 42 solder shorts.
AUTONOMATION - Transferring human intelligence to automated machinery so machines are able to detect the production of a single defective part and immediately stop themselves while asking for help.
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BACKGROUND VARIABLES - Variables which are of no experimental interest and are not held constant. Their effects are often assumed insignificant or negligible, or they are randomized to ensure that contamination of the primary response does not occur.
BATCH-AND-QUEUE - Producing more than one piece of an item and then moving those items forward to the next operation before they are all actually needed there. Thus items need to wait in a queue. Also called “Batch-and-Push.” Contrast with continuous flow.
BETA RISK - The probability of accepting the null hypothesis when, in reality, the alternate hypothesis is true.
BLOCKING VARIABLES - A relatively homogenous set of conditions within which different conditions of the primary variables are compared. Used to ensure that background variables do not contaminate the evaluation of primary variables.
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CAUSALITY - The principle that every change implies the operation of a cause.
CAUSATIVE - Effective as a cause.
CAUSE - That which produces an effect or brings about a change.
C-CHARTS - Charts which display the number of defects per sample.
CELL - Operating a true continuous flow on machines and workstations placed close together in the order of processing, sometimes in a “U” shape. Cell operators may handle multiple processes, and the number of operators is changed when the customer demand rate changes. The “U” shaped equipment layout is used to allow more alternatives for distributing the work elements among operators, and to permit the leadoff and final operations to be performed by the same operator.
CHAKU-CHAKU - A method of conducting single-piece flow in which the operators proceeds from machine to machine, taking the part from the previous operation and loading it in the next machine, then taking the part just removed from the machine and loading it in the following machine, etc. Literally, means “load-load” in Japanese.
CHARACTERISTIC - A definable or measurable feature of a process, product, or variable.
CENTRAL TENDENCY - Numerical average, e.g., mean, median, and mode; center line on a statistical process control chart.
CENTER LINE - The line on a statistical process control chart which represents the characteristic’s central tendency.
CLASSIFICATION - Differentiation of variables.
COMMON CAUSE - See RANDOM CAUSE.
CONFIDENCE LEVEL - The probability that a random variable x lies within a defined interval.
CONFIDENCE LIMITS - The two values that define the confidence interval.
CONFOUNDING - Allowing two or more variables to vary together so that it is impossible to separate their unique effects.
CONSUMERS RISK - Probability of accepting a lot when, in fact, the lot should have been rejected (see BETA RISK).
CONTINUOUS DATA - Numerical information at the interval of ratio level; subdivision is conceptually meaningful; can assume any number within an interval, e.g., 14.652 amps.
CONTINUOUS FLOW PRODUCTION - Items are produced and moved from one processing step to the next one piece-at-a-time. Each process makes only the one piece that the next process needs, and the transfer batch size is one. Also called “single-piece flow” or “one-piece flow.” Contrast with batch-and-queue.
CONTINUOUS RANDOM VARIABLE - A random variable which can assume any value continuously in some specified interval.
CONTROL CHART - A graphical rendition of a characteristic’s performance across time in relation to its natural limits and central tendency.
CONTROL SPECIFICATIONS - Specifications called for by the product being manufactured.
CTQ – Critical to Quality
CUTOFF POINT - The point which partitions the acceptance region from the reject region.
CYCLE TIME - How frequently an item or product actually is completed by a process, as timed by direct observation. Also, the time it takes an operator to go through all of his or her work elements before repeating them.
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DATA - Factual information used as a basis for reasoning, discussion, or calculation; often refers to quantitative information.
DEGREES OF FREEDOM - The number of independent measurements available for estimating a population parameter
DENSITY FUNCTION - The function which yields the probability that a particular random variable takes on any one of its possible values.
DEPENDENT VARIABLE - A Response Variable; e.g., y is the dependent or “Response” variable where Y=f (Xl. . . XN) variable.
DISCRETE RANDOM VARIABLE - A random variable which can assume values only from a definite number of discrete values.
DISTRIBUTIONS - Tendency of large numbers of observations to group themselves around some central value with a certain amount of variation or “scatter” on either side.
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EPEI - Refers to the “every-product-every interval,” which is a measure of production batch size. For example, if a machine is able to change over and produce the required quantity of all the high-running part types dedicated to it within three days, then the production batch size for each individual part type is about three days worth of parts. Thus this machine is making every part every (EPE) three days.
EFFECT - That which was produced by a cause.
EXPERIMENT - A test under defined conditions to determine an unknown effect; to illustrate or verify a known law; to test or establish a hypothesis.
EXPERIMENTAL ERROR - Variation in observations made under identical test conditions. Also called residual error. The amount of variation which cannot be attributed to the variables included in the experiment.
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FABRICATION PROCESSES – Segments of the value stream that respond to requirements from internal customers. Fabrication processes are often characterized by general-purpose equipment that changes over to make a variety of components for different downstream processes. Compare to “pacemaker process”.
FACTORS - Independent variables.
FIFO - Stands for “first in, first out,” which means that material produced by one process is used up in the same order by the next process. FIFO is one way to regulate a queue between two decoupled processes when a supermarket or continuous flow is impractical. A FIFO queue is filled by the supplying process and emptied by the customer process. When a FIFO queue gets full, the supplying process must stop producing until the customer process has used up some of the inventory.
FIVE S - Five terms beginning with ‘S’ utilized to create a workplace suited for visual control and lean production. ‘Seiri’ means to separate needed tools, parts, and instructions from unneeded materials and to remove the latter. ‘Seiton’ means to neatly arrange and identify parts and tools for ease of use. ‘Seiso’ means to conduct a cleanup campaign. ‘Seiketsu’ means to conduct seiri, seiton, and seiso at frequent, indeed daily, intervals to maintain a workplace in perfect condition. ‘Shitsuke’ means to form the habit of always following the first four S’s. In English, we use the five words: Sort, Set in Order, Shine, Standardize, and Sustain.
FIXED EFFECTS MODEL - Experimental treatments are specifically selected by the researcher. Conclusions only apply to the factor levels considered in the analysis. Inferences are restricted to the experimental levels.
FLOW - A main objective of the entire lean production effort, and one of the key concepts that passed directly from Henry Ford to Taiichi Ohno (Toyota’s production manager after WWII). Ford recognized that, ideally, production should flow continuously all the way from raw material to the customer and envisioned realizing that ideal through a production system that acted as one long conveyor.
FLUCTUATIONS - Variances in data, which are caused by a large number of, minute variations or differences.
FREQUENCY DISTRIBUTION - The pattern or shape formed by the group of measurements in a distribution.
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GENCHI GENBUTSU - “Go, see & confirm.”
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HEIJUNKA - The act of leveling the variety and/or volume of items produced at a process over a period of time. Used to avoid excessive batching of product types and/or volume fluctuations, especially at a pacemaker process.
HISTOGRAM - Vertical display of a population distribution in terms of frequencies; a formal method of plotting a frequency distribution.
HOMOGENEITY OF VARIANCE - The variances of the groups being contrasted are equal (as defined by statistical test of significant difference).
HOSHIN KANRI - A strategic decision-making tool for a firm’s executive team that focuses resources on the critical initiatives necessary to accomplish the business objectives of the firm. Hoshin Kanri unifies and aligns resources and establishes clearly measurable targets against which progress toward the key objectives is measured on a regular basis.
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INDEPENDENT VARIABLE - A controlled variable; a variable whose value is independent of the value of another variable.
INFORMATION FLOW - Data that tells a process what to do or produce.
INTERACTION - When the effects of a factor A are not the same at all levels of another factor B.
INSTABILITY - Unnaturally large fluctuations in a pattern.
INTERACTION - The tendency of two or more variables to produce an effect in combination which neither variable would produce if acting alone.
INTERVAL - Numeric categories with equal units of measure but no absolute zero point, i.e., quality scale or index.
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JIDOKA - See Autonomation.
JUST-IN-TIME - Producing or conveying only the items that are needed by the next process when they are needed and in the quantity needed
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KAIKAKU - Radical improvement of an activity to eliminate muda (waste), for example by reorganizing processing operations for a product so that instead of traveling to and from isolated “process villages,” the product proceeds through the operations in single-piece flow in one short space. Also called breakthrough kaizen, flow kaizen, and system kaizen.
KAIZEN - Continuously improving in incremental steps.
KANBAN - A signaling device that gives instruction for production or conveyance of items in a pull system. Can also be used to perform kaizen by reducing the number of kanban in circulation, which highlights line problems.
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LEAD TIME - The time required for one piece to move all the way through a process or value stream, from start to finish. Envision timing a marked item as it moves from beginning to end.
LINE CHARTS - Charts used to track the performance without relationship to process capability or control limits.
LOWER CONTROL LIMIT (LCL) - A horizontal dotted line plotted on a control chart which represents the lower limits of process capability.
LOWER SPECIFICATION LIMIT (LSL) – The lower limit of what the customer wants.
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MIXED EFFECTS MODEL - Contains elements of both the fixed and random effects models.
MATERIAL FLOW - Movement of physical product through the value stream.
MATERIAL HANDLERS - Production-support persons who travel repeatedly along scheduled routes within a facility to transfer materials, supplies, and parts in response to pull signals, and to make paced withdrawal of finished goods at pacemaker processes.
MATERIAL REQUIREMENTS PLANNING (MRP) - A computerized system typically used to determine the quantity and timing requirements for delivery and production of items. Using MRP specifically to schedule production at processes in a value stream results in push production, because any predetermined schedule is only an estimate of what the next process will actually need. Manufacturing Resource Planning - often called MRP II - expands MRP to include capacity planning, a finance interface to translate operations planning into financial terms, and a simulation tool to assess alternative production plans.
MILK RUN - Routing a delivery vehicle in a way that allows it to make pickups or drop-offs at multiple locations on a single travel loop, as opposed to making separate trips to each location.
MONUMENT - Any design, scheduling, or production technology with scale requirements necessitating that designs, order, and products be brought to the machines to wait in a queue for processing.
MUDA - See ‘Waste’
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NOMINAL - Unordered categories which indicate membership or non-membership with no implication of quantity, i.e., assembly area number one, part numbers, etc.
NONCONFORMING UNIT - A unit which does not conform to one or more specifications, standards, and/or requirements.
NONCONFORMITY - A condition within a unit which does not conform to some specific specification, standard, and/or requirement; often referred to as a defect; any given nonconforming unit can have the potential for more than one nonconformity.
NORMAL DISTRIBUTION - A continuous, symmetrical density function characterized by a bell-shaped curve, e.g., distribution of sampling averages.
NULL HYPOTHESIS - A tentative explanation which indicates that a chance distribution is operating; a contrast to the null hypothesis.
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ONE-SIDED ALTERNATIVE -The value of a parameter which has an upper bound or a lower bound, but not both.
OPERATION - An activity or activities performed on a product by a single machine. Contrast with ‘process’.
OPERATOR BALANCE CHART - A bar graph depicting the cycle times of each operator in a process to make one piece compared to takt time. Useful tool for cell balancing and creating continuous flow.
ORDINAL - Ordered categories (ranking) with no information about distance between each category, i.e., rank ordering of several measurements of an output parameter
ORDINATE - The vertical axis of a graph.
OVERPRODUCTION - Producing more, sooner or faster than is required by the next process.
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PACED WITHDRAWAL - A timed sequence of withdrawal of finished product from the pacemaker process. Paced withdrawal is a tool for pacing an assembly process and becoming aware of production problems within a pitch increment.
PACEMAKER PROCESS - A series of production steps, frequently at the downstream (customer) end of the value stream in a facility, which are dedicated to a particular product family and respond to orders from external customers. The pacemaker is the most important process in a facility because how you operate here determines how well you can serve the customer, and what the demand pattern is like for upstream fabrication processes.
PARAMETER - A constant defining a particular property of the density function of a variable.
PARETO DIAGRAM - A chart which ranks, or places in order, common occurrences.
P CHARTS - Charts used to plot percent defectives in a sample.
PERTURBATION - A non-random disturbance.
PERFECTION - The complete elimination of muda (waste) so that all activities along a value stream create value.
PITCH - When takt time is too short for a reasonable paced withdrawal it can be adjusted upward to a consistent increment of work called pitch, which becomes the basic unit of your production schedule for a product family. Pitch represents the frequency at which you withdraw finished goods from a pacemaker process as well as the corresponding amount of schedule you release to that process. Pitch is often calculated based on the customer’s ship container quantity.
POKA-YOKE - A mistake-proofing device to prevent defects from occurring.
POPULATION - A group of similar items from which a sample is drawn. Often referred to as the universe.
POWER OF AN EXPERIMENT - The probability of rejecting the null hypothesis when it is false and accepting the alternate hypothesis when it is true.
PREVENTION - The practice of eliminating unwanted variation a priori (before the fact), e.g., predicting a future condition from a control chart and then applying corrective action before the predicted event transpires.
PRIMARY CONTROL VARIABLES - The major independent variables used in the experiment.
PROBABILITY - The chance of something happening; the percent or number of occurrences over a large number of trials.
PROBABILITY OF AN EVENT - The number of successful events divided by the total number of trials.PROBLEM - A deviation from a specified standard.PROCESS - A series of individual operations required in order to create a design, completed order, or product.
PROCESS AVERAGE - The central tendency of a given process characteristic across a given amount of time or at a specific point in time.
PROCESS CONTROL CHART - Any of a number of various types of graphs upon which data are plotted against specific control limits.
PROCESS KAIZEN - Improvements made at an individual process or in a specific area. Sometimes called “point kaizen”.
PROCESS SPREAD - The range of values which a given process characteristic displays; this particular term most often applies to the range but may also encompass the variance. The spread may be based on a set of data collected at a specific point in time or may reflect the variability across a given amount of time.
PROCESS VILLAGES - The practice of grouping machines or activities by type of operation performed; for example, grinding machines or order-entry. Contrast with ‘cells’.
PROCESSING TIME - The time a product is actually being worked on in a machine or work area.
PRODUCERS RISK - Probability of rejecting a lot when, in fact, the lot should have been accepted (see ALPHA RISK).
PRODUCT FAMILY - A group of products that go through the same or similar downstream or “assembly” steps and equipment.
PRODUCTION SMOOTHING - See ‘Heijunka’
PULL SYSTEM - An alternative to scheduling individual processes, where the customer process withdraws the items it needs from a supermarket, and the supplying process produces to replenish what was withdrawn. Used to avoid push. See also kanban.
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QUEUE TIME - The time a product spends waiting in line for the next processing step.
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R CHARTS - Plot of the difference between the highest and lowest in a sample. Range control chart.
RANDOM - Selecting a sample so each item in the population has an equal chance of being selected; lack of predictability; without pattern.
RANDOM CAUSE - A source of variation which is random; a change in the source (”trivial many” variables) will not produce a highly predictable change in the response (dependent variable), e.g., a correlation does not exist; any individual source of variation results in a small amount of variation in the response; cannot be economically eliminated from a process; an inherent natural source of variation.
RANDOM EFFECTS MODEL - Experimental treatments are a random sample from a larger population of treatments. Conclusions can be extended to the population. Interference’s are not restricted to the experimental levels.
RANDOMNESS - A condition in which any individual event in a set of events has the same mathematical probability of occurrence as all other events within the specified set, i.e., individual events are not predictable even though they may collectively belong to a definable distribution.
RANDOM SAMPLE - One or more samples randomly selected from the universe (population).
RANDOM VARIABLE - A variable which can assume any value from a set of possible values.
RANDOM VARIATIONS - Variations in data which result from causes which cannot be pinpointed or controlled.
RANGE - The difference between the highest and lowest values in a set of values or “subgroup.”
RANKS - Values assigned to items in a sample to determine their relative occurrence in a population.
RATIO - Numeric scale which has an absolute zero point and equal units of measure throughout, i.e., measurements of an output parameter, i.e., amps.
REJECT REGION - The region of values for which the alternate hypothesis is accepted.
REPLICATION - Observations made under identical test conditions.
ROBUST - The condition or state in which a response parameter exhibits hermetically to external cause of a nonrandom nature; i.e., impervious to perturbing influence.
REPRESENTATIVE SAMPLE - A sample which accurately reflects a specific condition or set of conditions within the universe.
RESIDUAL ERROR - See EXPERIMENTAL ERROR.
RIGHT-SIZED TOOL - A design, scheduling, or production device that can be fitted directly into the flow of products within a product family so that production no longer requires unnecessary transport and waiting. Contrast with ‘monument’.
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SAMPLE - One or more observations drawn from a larger collection of observations or universe (population).
SCATTER DIAGRAMS - Charts which allow the study of correlation, e.g., the relationship between two variables.
SENSEI - A personal teacher with a mastery of a body of knowledge, in this case lean thinking techniques.
SIPOC – A basic flow diagram that includes suppliers, inputs, process, outputs, customers.
SIX SIGMA - Sigma is a letter in the Greek alphabet. The term “sigma” is used to designate the distribution or spread about the mean (average) of any process or procedure. For a business or manufacturing process, the sigma value is a metric that indicates how well that process is performing. The higher the sigma value, the better. Sigma measures the capability of the process to perform defect-free-work. A defect is anything that results in customer dissatisfaction. Sigma is a statistical unit of measure which reflects process capability. The sigma scale of measure is perfectly correlated to such characteristics as defects-per-unit, parts-per million defective, and the probability of a failure/error; 6-sigma means no more than 3.4 parts per million opportunities.
SPAGHETTI CHART - A map of the path taken by a specific product as it travels down the value stream in a mass-production organization, so-called because the product’s route typically looks like a plate of spaghetti.
SPC - Statistical Process Control. A method whereby data is collected and statistics used to understand process stability.
SPECIAL CAUSE - See ASSIGNABLE CAUSE.
STABLE PROCESS - A process which is free of assignable causes, e.g., in statistical control.
STANDARD DEVIATION - A statistical index of variability which describes the spread with a given data set.
STATISTICAL CONTROL - A quantitative condition which describes a process that is free of assignable/special causes of variation, e.g., variation in the central tendency and variance. Such a condition is most often evidenced on a control chart, i.e., a control chart which displays an absence of nonrandom variation.
STATISTICAL PROCESS CONTROL - The application of statistical methods and procedures relative to a process and a given set of standards.
STANDARD WORK - A precise description of each work activity specifying cycle time, takt time, the work sequence of specific tasks, and the minimum inventory of parts on hand needed to conduct the activity.
SUBGROUP - A logical grouping of objects or events which displays only random event-to-event variations, e.g., the objects or events are grouped to create homogenous groups free of assignable or special causes. By virtue of the minimum within group variability, any change in the central tendency or variance of the universe will be reflected in the “subgroup-to-subgroup’ variability.
SUPERMARKET - A controlled inventory of items that is used to schedule production at an upstream process.
SYMPTOM - That which serves as evidence of something not seen.
SYSTEM - That which is connected according to a scheme.
SYSTEM KAIZEN - Improvement aimed at an entire value stream.
SYSTEMATIC VARIABLES - A pattern which displays predictable tendencies.
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TAKT TIME - The rate of customer demand. How often the customer requires one finished item. Takt time is used to design assembly and pacemaker processes, to assess production conditions, to calculate pitch, to develop material handling containerization and routes, to determine problem - response requirements, and so on. Takt is the heartbeat of a lean system. Takt time is calculated by dividing production time by the quantity the customer requires in that time.
THEORY - A plausible or scientifically acceptable general principle offered to explain phenomena.
TEST OF SIGNIFICANCE - A procedure to determine whether a quantity subjected to random variation differs from a postulated value by an amount greater than that due to random variation alone.
TOTAL PRODUCTIVE MAINTENANCE (TPM) - A series of methods, originally pioneered by Nippondenso (a member of the Toyota group), to ensure that every machine in a production process is always able to perform its required tasks so that production is never interrupted.
TWO-SIDED ALTERNATIVE - The values of a parameter which designate an upper and lower bound.
TYPE I ERROR - See ALPHA RISK.
TYPE II ERROR - See BETA RISK.
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UNNATURAL PATTERN - Any pattern in which a significant number of the measurements do not group them-selves around a center line; when the pattern is unnatural, it means that outside disturbances are present and are affecting the process.
UPPER CONTROL LIMIT (UCL) - A horizontal line on a control chart (usually dotted) which represents the upper limits of process capability.
UPPER SPECIFICATION LIMIT (USL) – The upper limit of what the customer wants.
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VALUE - A product or service’s capability provided to a customer at the right time, at an appropriate price, as defined in each case by the customer.
VALUE ADDED TIME - Time for those work elements that transform the product in a way the customer is willing to pay for.
VALUE STREAM - All activities, both value added and non value added, required to bring a product from raw material into the hands of the customer, a customer requirement from order to delivery, and a design from concept to launch. Value stream improvement usually begins at the door-to-door level within a facility, and then expands outward to eventually encompass the full value stream.
VALUE STREAM LOOPS - Segments of a value stream whose boundaries are typically marked by supermarkets. Breaking a value stream into loops is a way to divide future state implementation into manageable pieces.
VALUE STREAM MANAGER - Person responsible for creating a future state map and leading door-to-door implementation of the future state for a particular product family. Makes change happen across departmental and functional boundaries.
VALUE STREAM MAPPING - A pencil-and-paper tool used in two stages: a) Follow a product’s production path from beginning to end and draw a visual representation of every process in the material and information flows. b) Then draw a future state map of how value should flow. The most important map is the future state map.
VARIABLE - A characteristic that may take on different values.
VARIABLES DATA - Numerical measurements made at the interval or ratio level; quantitative data, e.g., ohms, voltage, diameter; subdivisions of the measurement scale are conceptually meaningful, e.g., 1.6478 volts.
VARIATION - Any quantifiable difference between individual measurements; such differences can be classified as being due to common causes (random) or special causes (assignable).
VARIATION RESEARCH - Procedures, techniques, and methods used to isolate one type of variation from another (for example, separating product variation from test variation).
VISUAL CONTROL - The placement in plain view of all tools, parts, production activities, and indicators of production system performance, so that everyone involved can understand the status of the system at a glance.
VOC – Voice of the customer
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WASTE - Any activity that consumes resources but creates no value for the customer.
WATER SPIDER - See “Material Handlers”
WIP - Stands for “work in process.” Any inventory between raw material and finished goods.
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X (Bar) & R CHARTS - A control chart which is a representation of process capability over time; displays the variability in the process average and range across time.
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