GLOSSÁRIO SIX SIGMA C O M U N I D A D E L E A N T H I N K I N G 1 de 28 Benchmarking An improvement process whereby a company measures its performance against that of best-in-class companies, determines how those companies achieved their performance levels, and uses the information to improve its own performance. Black Belt Full-time Six Sigma project leader who is certified following a four-month training and application program and successful completion of two Six Sigma Projects, the first under the guidance of a Master Black Belt, the second more autonomously. “Breakthrough Strategy” The data driven, Six Sigma process improvement strategy involving four phases: Measure, Analyze, Improve and Control. Cause That which produces an effect or brings about change. Cause-And-Effect Diagram A schematic sketch, usually resembling a fishbone, which illustrates the main causes and subcauses leading to an effect (symptom). Also known as Fishbone Diagram. Champion Member of the senior Aircraft Engines staff who has undergone extensive Six Sigma training. Champions provide direction, resources and support to the Six Sigma effort and approve and review projects. Characteristic A definable or measurable feature of a process, product or variable. Control Chart A graphical rendition of a characteristic’s performance across time in relation to its natural limits and central tendency. Correlation The determination of the effect of one variable upon another in a dependent situation. Cp A widely used capability index for process capability studies. It may range in value from zero to infinity with a larger value indicating a more capable process. Six Sigma represents Cp of 2.0.
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Benchmarking
An improvement process whereby a company measures its performance against that of
best-in-class companies, determines how those companies achieved their performance
levels, and uses the information to improve its own performance.
Black Belt
Full-time Six Sigma project leader who is certified following a four-month training and
application program and successful completion of two Six Sigma Projects, the first under
the guidance of a Master Black Belt, the second more autonomously.
“Breakthrough Strategy”
The data driven, Six Sigma process improvement strategy involving four phases:
Measure, Analyze, Improve and Control.
Cause
That which produces an effect or brings about change.
Cause-And-Effect Diagram
A schematic sketch, usually resembling a fishbone, which illustrates the main causes and
subcauses leading to an effect (symptom). Also known as Fishbone Diagram.
Champion
Member of the senior Aircraft Engines staff who has undergone extensive Six Sigma
training. Champions provide direction, resources and support to the Six Sigma effort and
approve and review projects.
Characteristic
A definable or measurable feature of a process, product or variable.
Control Chart
A graphical rendition of a characteristic’s performance across time in relation to its
natural limits and central tendency.
Correlation
The determination of the effect of one variable upon another in a dependent situation.
Cp
A widely used capability index for process capability studies. It may range in value from
zero to infinity with a larger value indicating a more capable process. Six Sigma
represents Cp of 2.0.
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Cpk
An index combining Cp and K (Difference between the process mean and the specification
mean) to determine whether the process will produce units within tolerance. Cpk is
always less than or equal to Cp. When the process is centered at nominal, Cpk is equal to
Cp.
Critical To Quality (CTQ)
An element of a design or a characteristic of a part that is essential to quality in the eyes
of the customer, formerly known as a key quality characteristic (KQC).
Data
Factual information used as a basis for reasoning, discussion or calculation; often refers
to quantitative information.
Defect
A failure to meet an imposed requirement on a single quality characteristic or a single
instance of nonconformance to the specification.
Defects Per Million Opportunities (DPMO)
The number of defects counted, divided by the actual number of opportunities to make a
defect, then multiplied by one million. A direct measure of sigma level.
Defects Per Unit (DPU)
The number of defects counted, divided by the number of products or characteristics
produced. A process of counting and reducing defects as an initial step toward Six Sigma
quality.
Defective
A unit of product containing one or more defects.
Design For Manufacturability (DFM)
A concept in which products are designed within the current manufacturing process
capability to ensure that engineering requirements are met during production.
Design of Experiments (DOE)
Statistical experimental designs to economically improve product and process quality. A
major tool used during the “Improve Phase” of Six Sigma methodology.
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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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
A test under defined conditions to determine an unknown effect; to illustrate or verify a
known law; to test or establish a hypothesis.
“Factory” Processes
For Six Sigma purposes, defined as design, manufacturing, assembly or test processes
which directly impact hardware (see also transaction processes).
Fishbone Diagram
A schematic sketch, usually resembling a fishbone, which illustrates the main causes and
subcauses leading to an effect (symptom). Also known as Cause-And-Effect Diagram.
Failure Mode Effects Analysis (FMEA)
A process in which each potential failure mode in every sub-item of an item is analyzed
to determine its effect on other sub-items and on the required function of the item.
“Five Ms”
Major sources of variation: manpower, machine, method, material and measurement.
Additionally, “environment” is considered to be a source of variation.
Frequency Distribution
The pattern or shape formed by the group of measurements in a distribution.
Gage Repeatability & Reproducibility (Gage R&R)
A measurement system evaluation to determine equipment variation and appraiser
variation. This study is critical to ensure that the collected data is accurate.
Histogram
Vertical display of a population distribution in terms of frequencies; a formal method of
plotting a frequency distribution.
Independent Variable
A controlled variable; a variable whose value is independent of the value of another
variable.
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Interaction
When the effects of a factor A are not the same at all levels of another factor B.
Lower Control Limit
A horizontal dotted line plotted on a control chart which represents the lower process
limit capabilities of a process.
Master Black Belt
An expert in quality techniques specially trained to advise leaders, facilitate quality teams
and accelerate process improvement. Master Black Belts select, train and mentor Black
Belts; develop and implement the Six Sigma deployment plan; and select and ensure
completion of Six Sigma projects.
Nonconformity
A condition within a unit which does not conform to some 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.
Pareto Diagram
A chart which ranks, or places in order, common occurrences.
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 trails.
Process
A particular method of doing something, generally involving a number of steps or
operations.
Process Capability
The relative ability of any process to produce consistent results centered on a desired
target value when measured over time.
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Process Control Chart
Any of a number of various types of graphs upon which data are plotted against specific
control limits.
Process Map
Flow chart to analyze a process by breaking it down into its component steps, and then
gaining a better understanding of the process, step-by-step.
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.
Quality Functional Deployment (QFD)
Structured methodology to identify and translate customer needs and wants into technical
requirements and measurable features and characteristic. This tool is used to identify
Critical to Quality Characteristics (CTQCs).
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 Variation
Variations in data which result from causes which cannot be pinpointed or controlled.
Regression Analysis
A statistical technique for determining the relationship between one response and one or
more independent variables.
Robust
The condition or state in which a response parameter exhibits hermetically to external
cause of a nonrandom nature; e.g., impervious to perturbing influence.
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Rolled Yield
The combined resulting quality level, stated as a percent acceptable, that occurs when
several processes known to produce defects at some rate are combined to produce a
product. For example, a product that requires 100 steps, each of which produces a yield
of 98.78% will produce a rolled yield of 0%, that is, no acceptable products.
Scatter Diagram
A diagram that displays the relationships between two variables.
Sigma
Standard deviation; an empirical measure based on the analysis of random variation in a
standard distribution of values; a uniform distance from the mean or average value such
that 68.26% of all values are within 1 sigma on either side of the mean, 95.44% are
within 2 sigma, 99.73% are within 3 sigma, 99.9% are within 4 sigma and so forth.
Sigma Level
A statistical estimate of the number of defects that any process will produce equivalent to
defects per million opportunities for that process.
Six Sigma Quality
A combination of verified customer requirements reflected in robust designs and matched
to the capability of production processes that creates products with fewer then 3.4 defects
per million opportunities to make a defect. World-class quality. A collection of tools
and techniques for raising quality to worked-class levels.
Stable Process
A process which i free of assignable causes, e.g., in statistical control.
Standard Deviation
A statistical index of variability which describes the spread.
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.
Statistical Process Control
The application of statistical methods and procedures relative to a process and a given set
of standards.
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Transaction Processes
For Six Sigma purposes, defined as any business process that contributes to customer
satisfaction or impacts operating efficiency and which is designated by a vice president or
by GE Corporate as a focus for process improvement. Such efforts will be led by the
process owner, with teams being led by specially trained transaction project leaders
and/or by certified Black Belts.
Transaction Project Leader
An individual designated to lead a transaction process improvement project. Transaction
project leaders attend a four-day course in specific Six Sigma tools and tactics.
Upper Control Limit
A horizontal line on a control chart (usually dotted) which represents the upper limits of
process capability.
Variable
A characteristic that may take on different values.
Variables Data
A numerical measurement 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).
“Xs”
Designation in Six Sigma terminology for those variables which are independent, root
causes; as opposed to “Ys” which are dependent outputs of a process. Six Sigma focuses
on measuring and improving Xs, to see subsequent improvement in Ys.
X & 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.
“Ys”
Designation in Six Sigma terminology for those variables which are dependent outputs of
a process, as opposed to “Xs” which are independent root causes.