ASTM E2782-17(2022)e1

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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Designation: E2782 − 17 (Reapproved 2022) An American National Standard
Standard Guide for
Measurement Systems Analysis (MSA)
This standard is issued under the fixed designation E2782; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
ε NOTE—Subsection 3.1 was corrected editorially in July 2022.
1. Scope 3. Terminology
3.1 Definitions—Unless otherwise noted in this standard, all
1.1 This guide presents terminology, concepts, and selected
terms relating to quality and statistics are defined in Terminol-
methods and formulas useful for measurement systems analy-
ogy E456.
sis (MSA). Measurement systems analysis may be broadly
described as a body of theory and methodology that applies to 3.1.1 accepted reference value, n—a value that serves as an
the non-destructive measurement of the physical properties of agreed-upon reference for comparison, and which is derived
manufactured objects. as: (1) a theoretical or established value, based on scientific
principles, (2) an assigned or certified value, based on experi-
1.2 Units—The system of units for this guide is not speci-
mental work of some national or international organization, or
fied. Dimensional quantities in the guide are presented only as
(3) a consensus or certified value, based on collaborative
illustrations of calculation methods and are not binding on
experimental work under the auspices of a scientific or
products or test methods treated.
engineering group. E177
1.3 This standard does not purport to address all of the
3.1.2 calibration, n—process of establishing a relationship
safety concerns, if any, associated with its use. It is the
between a measurement device and a known standard value(s).
responsibility of the user of this standard to establish appro-
3.1.3 gage, n—device used as part of the measurement
priate safety, health, and environmental practices and deter-
process to obtain a measurement result.
mine the applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accor- 3.1.4 measurement process, n—process used to assign a
dance with internationally recognized principles on standard-
number to a property of an object or other physical entity.
ization established in the Decision on Principles for the
3.1.4.1 Discussion—The term “measurement system” is
Development of International Standards, Guides and Recom-
sometimes used in place of measurement process. (See 3.1.6.)
mendations issued by the World Trade Organization Technical
3.1.5 measurement result, n—number assigned to a property
Barriers to Trade (TBT) Committee.
of an object or other physical entity being measured.
3.1.5.1 Discussion—Theword“measurement”isusedinthe
2. Referenced Documents
same sense as measurement result.
2.1 ASTM Standards:
3.1.6 measurement system, n—the collection of hardware,
E177 Practice for Use of the Terms Precision and Bias in
software, procedures and methods, human effort, environmen-
ASTM Test Methods
tal conditions, associated devices, and the objects that are
E456 Terminology Relating to Quality and Statistics
measured for the purpose of producing a measurement.
E2586 Practice for Calculating and Using Basic Statistics
3.1.7 measurement systems analysis (MSA), n—any of a
E2587 Practice for Use of Control Charts in Statistical
number of specialized methods useful for studying a measure-
Process Control
ment system and its properties.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 appraiser, n—the person who uses a gage or measure-
This guide is under the jurisdiction of ASTM Committee E11 on Quality and
Statistics and is the direct responsibility of Subcommittee E11.50 on Metrology.
ment system.
Current edition approved May 15, 2022. Published May 2022. Originally
3.2.2 discrimination ratio, n—statistical ratio calculated
approved in 2011. Last previous edition approved in 2017 as E2782 – 17. DOI:
10.1520/E2782-17R22E01.
from the statistics from a gage R&R study that measures the
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
number of 97 % confidence intervals, constructed from gage
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
R&R variation, that fit within six standard deviations of true
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. object variation.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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E2782 − 17 (2022)
3.2.3 distinct product categories, n—alternate meaning of making go hand in hand and that is why the quality of any
the discrimination ratio. measurement is important—for data originate from a measure-
ment process. This guide presents selected concepts and
3.2.4 gage consistency, n—constancy of repeatability vari-
methods useful for describing and understanding the measure-
ance over a period of time.
ment process.This guide is not intended to be a comprehensive
3.2.4.1 Discussion—Consistency means that the variation
survey of this topic.
within measurements of the same object (or group of objects)
under the same conditions by the same appraiser behaves in a
4.2 Any measurement result will be said to originate from a
state of statistical control as judged, for example, using a
measurementprocessorsystem.Themeasurementprocesswill
control chart. See Practice E2587.
consist of a number of input variables and general conditions
that affect the final value of the measurement. The process
3.2.5 gage performance curve, n—curve that shows the
variables, hardware and software and their properties, and the
probability of gage acceptance of an object given its real value
human effort required to obtain a measurement constitute the
or the probability that an object’s real measure meets a
measurement process. A measurement process will have sev-
requirement given the measurement of the object.
eral properties that characterize the effect of the several
3.2.6 gage R&R, n—combined effect of gage repeatability
variables and general conditions on the measurement results. It
and reproducibility.
isthepropertiesofthemeasurementprocessthatareofprimary
3.2.7 gage resolution, n—degree to which a gage can
interest in any such study. The term “measurement systems
discriminate between differing objects.
analysis” or MSAstudy is used to describe the several methods
3.2.7.1 Discussion—The smallest difference between two
used to characterize the measurement process.
objects that a gage is capable of detecting is referred to as its
NOTE 1—Sample statistics discussed in this guide are as described in
finiteresolutionproperty.Forexample,alinearscalegraduated Practice E2586; control chart methodologies are as described in Practice
E2587.
in tenths of an inch is not capable of discriminating between
objects that differ by less than 0.1 in. (0.25 cm).
5. Characteristics of a Measurement System (Process)
3.2.8 gage stability, n—absence of a change, drift, or erratic
5.1 Measurement has been defined as “the assignment of
behavior in bias over a period of time.
numbers to material objects to represent the relations existing
3.2.8.1 Discussion—Stability means that repeated measure-
among them with respect to particular properties. The number
ments of the same object (or average of a set of objects) under
assigned to some particular property serves to represent the
the same conditions by the same appraiser behave in a state of
relative amount of this property associated with the object
statistical control as judged for example by using a control
concerned.” (1)
chart technique. See Practice E2587.
5.2 Ameasurement system may be described as a collection
3.2.9 linearity, n—difference or change in bias throughout
of hardware, software, procedures and methods, human effort,
theexpectedoperatingrangeofagageormeasurementsystem.
environmental conditions, associated devices, and the objects
3.2.10 measurement error, n—error incurred in the process
that are measured for the purpose of producing a measurement.
of measurement.
In the practical working of the measurement system, these
3.2.10.1 Discussion—As used in this guide, measurement
factors combine to cause variation among measurements of the
error includes one or both of R&R types of error.
same object that would not be present if the system were
3.2.11 repeatability conditions, n—in a gage R&R study,
perfect. A measurement system can have varying degrees of
conditionsinwhichindependentmeasurementsareobtainedon
each of these factors, and in some cases, one or more factors
identical objects, or a group of objects, by the same operator
may be the dominant contributor to this variation.
using the same measurement system within short intervals of
5.2.1 A measurement system is like a manufacturing pro-
time.
cess for which the product is a supply of numbers called
3.2.11.1 Discussion—As used in this guide, repeatability is
measurement results. The measurement system uses input
often referred to as equipment variation or EV.
factors and a sequence of steps to produce a result. The inputs
are just varying degrees of the several factors described in 5.2
3.2.12 reproducibility conditions, n— in a gage R&R study,
including the objects being measured. The sequence of process
conditions in which independent test results are obtained with
steps are that which would be described in a method or
the same method, on identical test items by different operators.
procedure for producing the measurement. Taken as a whole,
3.2.12.1 Discussion—As used in this guide, reproducibility
the various factors and the process steps work collectively to
is often referred to as appraiser variation or AV. This term is
form the measurement system/process.
also used in a broader sense in Practice E177.
5.3 An important consideration in analyzing any measure-
4. Significance and Use
ment process is its interaction with time. This gives rise to the
properties of stability and consistency. A system that is stable
4.1 Many types of measurements are made routinely in
and consistent is one that is predictable, within limits, over a
research organizations, business and industry, and government
period of time. Such a system has properties that do not
and academic agencies. Typically, data are generated from
experimentaleffortorasobservationalstudies.Fromsuchdata,
management decisions are made that may have wide-reaching
The boldface numbers in parentheses refer to the list of references at the end of
social, economic, and political impact. Data and decision this standard.
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E2782 − 17 (2022)
deteriorate with time (at least within some set time period) and
is said to be in a state of statistical control. Statistical control,
stability and consistency, and predictability have the same
meaning in this sense. Measurement system instability and
inconsistency will cause further added overall variation over a
period of time.
5.3.1 In general, instability is a common problem in mea-
surement systems. Mechanical and electrical components may
wear or degrade with time, human effort may exhibit increas-
ing fatigue with time, software and procedures may change
FIG. 2 Reproducibility Concept
with time, environmental variables will vary with time, and so
forth. Thus, measurement system stability is of primary con-
homogeneous population, among several laboratories or as
cern in any ongoing measurement effort.
measured using several systems.
5.4 There are several basic properties of measurement
5.4.2.1 Reproducibility may include different equipment
systems that are widely recognized among practitioners. These
and measurement conditions. This broader interpretation has
are repeatability, reproducibility, linearity, bias, stability,
attached “reproducibility conditions” and shall be defined and
consistency, and resolution. In studying one or more of these
interpreted by the user of a measurement system. (In Practice
properties,thefinalresultofanysuchstudyissomeassessment
E177, reproducibility includes interlaboratory variation.)
of the capability of the measurement system with respect to the
5.4.3 Bias is the difference between a standard or accepted
property under investigation. Capability may be cast in several
reference value for an object, often called a “master,” and the
ways, and this may also be application dependent. One of the
average value of a sample of measurements of the object(s)
primary objectives in any MSA effort is to assess variation
under a fixed set of conditions (see Fig. 1).
attributabletothevariousfactorsofthesystem.Allofthebasic
5.4.4 Linearity is the change in bias over the operational
properties assess variation in some form.
range of the measurement system. If the bias is changing as a
5.4.1 Repeatabilityisthevariationthatresultswhenasingle
function of the object being measured, we would say that the
object is repeatedly measured in the same way, by the same
system is not linear. Linearity can also be interpreted to mean
appraiser, under the same conditions (see Fig. 1). The term
that an instrument response is linearly related to the character-
“precision” also denotes the same concept, but “repeatability”
istic being measured.
is found more often in measurement applications. The term
5.4.5 Stability is variation in bias with time, usually a drift
“conditions” is sometimes combined with repeatability to
or trend, or erratic behavior.
denote “repeatability conditions” (see Terminology E456).
5.4.6 Consistency is the change in repeatability with time.A
5.4.1.1 The phrase “intermediate precision” is also used (for
system is consistent with time when the standard deviation of
example, see Practice E177). The user of a measurement
the repeatability error remains constant. When a measurement
system shall decide what constitutes “repeatability conditions”
system is stable and consistent, we say that it is a state of
or “intermediate precision conditions” for the given applica-
statistical control.
tion. Typically, repeatability conditions for MSA will be as
5.4.7 The resolution of a measurement system has to do
described in 5.4.1.
with its ability to discriminate between different objects. A
5.4.2 Reproducibility is defined as the variation among
system with high resolution is one that is sensitive to small
average values as determined by several appraisers when
chang
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