ASTM E2480-07

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:E2480–07
Standard Practice for
Conducting an Interlaboratory Study to Determine the
Precision of a Test Method with Multi-Valued Measurands
This standard is issued under the fixed designation E2480; 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.
1. Scope priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
1.1 This practice describes the techniques for planning,
conducting, and analyzing the results of an interlaboratory
2. Referenced Documents
study (ILS) conducted for certain test methods within Com-
2.1 ASTM Standards:
mittee E12.
E177 Practice for Use of the Terms Precision and Bias in
1.2 This practice does not concern itself with the develop-
ASTM Test Methods
ment of the test method but rather with the gathering of the
E284 Terminology of Appearance
information needed for the precision and bias statement after
E691 Practice for Conducting an Interlaboratory Study to
the completion of development of the test method. The data
Determine the Precision of a Test Method
obtained in the ILS may indicate, however, that further effort is
E1345 Practice for Reducing the Effect of Variability of
needed to improve the test method.
Color Measurement by Use of Multiple Measurements
1.3 Thispracticeisconcernedexclusivelywithtestmethods
that derive a multi-valued measurand, such as, but not limited
3. Terminology
to, spectral reflectance, transmittance function, tristimulus
3.1 Definitions—For color and appearance terms, see Ter-
values, or RGB values. Variation in measurements of such
minology E284.
multi-valued measurands are usually analyzed by reducing the
3.2 Definitions of Terms Specific to This Standard:
data to a single-valued parameter, such as color difference, DE.
3.2.1 precision and bias, n—when a test method is applied
1.4 This practice covers methods of dealing with the non-
to a large number of specimens that are as nearly alike as
normal distribution of the variation of sets of color-differences.
possible, the test results obtained nevertheless will not all have
This is done so that the user may derive valid statistics from
the same values.Ameasure of the degree of agreement among
such non-normal distributions.
these test results describes the precision of the test method for
1.5 This practice does not cover test methods, even in
that material. This practice is designed only to estimate the
Committee E12, whose measurands are single-valued, or
precision of a test method. However, when accepted reference
whose variations are known to be normally distributed. Task
values are known for the materials being tested, the test result
groups involved with such test methods are referred to Practice
data obtained in accordance with this practice may be used to
E691 which contains preferable methods of analyzing data
estimate the bias of the test method. For a discussion of bias
with those properties.
estimation, see Practice E177.
1.6 This practice is not intended to establish a method for
3.2.2 repeatability and reproducibility, n—the term repeat-
estimating possible color-difference tolerances.
abilityconcernsthevariabilitybetweenindependenttestresults
1.7 The values stated in SI units are to be regarded as the
obtained within a single laboratory in the shortest practical
standard. The values given in parentheses are for information
period of time by a single operator applying the test method
only.
with a specific set of test apparatus using test specimens taken
1.8 This standard does not purport to address all of the
at random from a single quantity of homogeneous material
safety concerns, if any, associated with its use. It is the
obtained, or prepared, for the ILS. The term reproducibility
responsibility of the user of this standard to establish appro-
concerns the variability between single test results obtained in
different laboratories, each by a different operator, each of
This practice is under the jurisdiction of ASTM Committee E12 on Color and
Appearance and is the direct responsibility of Subcommittee E12.93 on Precision For referenced ASTM standards, visit the ASTM website, www.astm.org, or
and Bias. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Current edition approved July 1, 2007. Published August 2007. DOI: 10.1520/ Standards volume information, refer to the standard’s Document Summary page on
E2480-07. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E2480–07
whom has applied the test method to specimens taken at ILS. The task group should decide on the number of laborato-
random from a single quantity of homogeneous material ries, materials, and test results for the ILS. The task group
obtained, or prepared, for the ILS. should obtain a statement of willingness to participate from
3.2.2.1 Discussion—The above single operator and single each of the participating laboratories. In addition, the task
apparatus requirement, as specified in 3.2.2, means that for a group should obtain, randomize, and distribute the specimens
particular step in the measurement process the same combina- to be tested.
tionofoperatorandapparatusisusedtoobtaineverytestresult 6.2 ILS Coordinator—The task group must appoint one
on every specimen. Thus, one operator could prepare and individual to act as overall coordinator of the ILS. This person
mount the specimen, another actuate the measurements, and hasresponsibilityfordistributingthematerialsandprotocolsto
still another record the value of the result. the laboratories, and for receiving the test result reports from
3.2.2.2 Discussion—The shortest practical period of time the laboratories.
means that the test results are obtained in a time not less than 6.3 Statistician:
normal testing and not so long as to permit significant changes 6.3.1 The test method task group should obtain the assis-
in material, equipment, calibration, or environment. tance of a person familiar with the statistical procedures of this
3.2.2.3 Discussion—The requirement that the measure- practice and with the materials being tested. When no such
ments be independent means that a single test determination person is available, the task group should obtain the assistance
begins with the mounting of the specimen on the sample port of a statistician who has experience in practical work with data
or in the transmission compartment, and ends with the removal from materials. Task group members need not be members of
of the test specimen from the port or compartment. All ASTM.
measurements are made with replacement. 6.3.2 The calculation of the statistics for each material may
3.2.2.4 Discussion—The requirement for different laborato- be readily done by persons not having knowledge of statistics,
ries does not exclude the case where more than one instrument but having basic knowledge of calculating and computers.
resides in the same company, laboratory, or room, provided 6.4 Laboratory ILS Supervisor—Each participating labora-
that each has an independent and separate calibration traceabil- tory must have an ILS supervisor to oversee the conduct of the
ity path from each other. ILS within the laboratory and to communicate with the ILS
3.2.3 test method and protocol, n—in this practice, the term Coordinator. This supervisor’s name should be obtained at the
testmethodappliestoboththeactualmeasurementprocessand time that the laboratory states its willingness to participate.
the written description of the process, while the term protocol
refers to the written instructions given the participants for 7. Basic Design
conducting the ILS.
7.1 Keep the design as simple as possible in order to obtain
3.2.4 test specimens, n—the portion of the material being
estimates of within- and between-laboratory variability that are
tested needed for obtaining a single test determination is called
free of secondary effects. The basic design is represented by a
a test specimen.Asingle test specimen may be measured more
two-way classification table, in which the rows represent the
than once and the results combined to produce a test result if
laboratories, and the columns represent the materials, and each
the protocol or test method so specifies.
cell (the intersection of a row and a column) contains a test
result made by a particular laboratory on a particular material.
4. Summary of Practice
4.1 The procedure presented in this practice consists of
8. Test Method
three steps: planning the interlaboratory study, guiding the
8.1 A written version of the test method (but not one
testing phase of the study, and analyzing the test result data.
necessarily as yet published as an ASTM standard) must have
The analysis includes the calculation of the numerical mea-
been developed and be distributed with the protocol if other-
sures of precision of the test method applying to both within-
wise unavailable to the participating laboratories.
laboratory repeatability and between-laboratory reproducibil-
8.2 The test method should have been subjected to a
ity.
screening procedure, in order that some experience with the
test method has been obtained before an ILS is conducted.Test
5. Significance and Use
conditionsthataffectthetestresults,ifany,shouldbeidentified
5.1 ASTM regulations require precision statements for all
and a statement of the needed degree of control of these
test methods in terms of repeatability and reproducibility. This
conditions should be provided. In addition, the test method, or
practice may be used in obtaining the information needed to
the protocol, should specify to how many digits of precision
prepareaprecisionstatementinaccordancewithPracticeE177
each test result is to be measured.
and the “Blue Book.”
8.3 The test method should specify the calibration proce-
dure and the frequency of calibration.
PLANNING THE INTERLABORATORY STUDY (ILS)
6. ILS Membership 9. Laboratories
6.1 Task Group—Either the task group that developed the 9.1 Number of Laboratories—AnILSshouldberunwithno
test method or a special task group formed specifically for the fewer than 8 laboratories. It is recommended that the number
purpose must have overall responsibility for the funding, of laboratories be set at 10, and it is desirable that more
staffing, design, and decision-making with regard to data in the laboratories be included if available in order that the ILS is
E2480–07
conducted with a reasonable cross-section of competent labo- 12. Protocol
ratories. Under no circumstances, allowing for attrition, should
12.1 Prepare a written protocol containing instructions for
the final statement of precision of a test method be based on
the participating laboratories to follow. Clearly identify the
fewer than 6 laboratories when the requisite three materials are
specific version of the test method being studied. If the test
employed.
method allows options in apparatus or procedure, clearly
9.1.1 Under some circumstances and with some test meth-
specify which option has been selected for conducting the ILS.
ods, it may be impossible to obtain the necessary six labora-
12.2 Cite the name, address, telephone number, and E-mail
tories. Under these conditions, it is permissible to proceed with
addressoftheILSCoordinator.Urgetheparticipantstocallthe
the supplementation of additional materials to make up for the
coordinator with any questions that may arise as to the conduct
loss of degrees of freedom using the following schedule of
of the ILS.
materials and laboratories:
12.3 Request that the participating laboratory keep a record
Number of Labs Required Minimum
(or log) of any special events that arise during any phase of the
Number of Materials
testing. This record should include any specific aspects of the
apparatus, calibration, or procedure that ought to be commu-
nicated to the task group to allow them to prepare the final
research report on the ILS.
9.2 The ILS should not be restricted to a group of labora-
toriesjudgedtobeexceptionallyqualifiedandequippedforthe
12.4 Supply data sheets for each material for recording the
ILS. Precision estimates for a test method should be obtained
raw data as observations are made, or if it would be more
through conditions where laboratories are competent and
convenient for the participating laboratory, specify the format,
personnelareoperatingunderconditionsthatwillprevailwhen
includingthenumberofsignificantdigitstoberecorded,ofthe
the test method is used in practice.
data to be returned to the coordinator.
10. Materials
CONDUCTING THE TESTING PHASE OF THE ILS
10.1 The term material means anything with a property that
13. Full Scale Run
can be measured. Different materials having the same property
may be expected to have different levels of the property,
13.1 Material Preparation and Distribution:
meaning higher or lower levels of the property.
13.1.1 Sample Preparation and Labeling—Prepare enough
10.2 The ILS should include a minimum of three different
material to supply 50 % more than needed by the number of
materials each with a different levels of the property under test,
laboratories committed to the ILS. Label each test specimen
and to be broadly applicable more than three materials of
with the laboratory number and a letter designator referring to
differing levels should be assessed.
the material. Thus, if 8 laboratories were participating in a test
10.3 The materials involved in any one ILS should differ
concerning 6 levels of material (perhaps different colors of the
primarily in the differing levels of the property being assessed same material), then specimens would be labeled from 1A
by the test method. When it is known, or suspected, that
through 1F, to 8A through 8F with the other laboratories
different classes of materials will exhibit different levels of similarly labeled between these limits.
precision when tested by the test method, consideration should
13.1.2 Randomization—Prepare a table for each laboratory
begiventoconductingseparateinterlaboratorystudiesforeach
that randomizes the order in which that laboratory is to test its
class of material.
set of specimens. Using the above example, the random table
10.4 The ILS should not be restricted to materials that are for the first laboratory would include the 6 specimens from 1A
judged to be exceptionally qualified for the ILS. Precision
to 1F in random order. Each of the 8 tables for the 8
estimates for a test method should be obtained through
...