ASTM C802-96(2008)e1

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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.
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Designation:C802–96 (Reapproved 2008)
Standard Practice for
Conducting an Interlaboratory Test Program to Determine
the Precision of Test Methods for Construction Materials
This standard is issued under the fixed designation C802; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
´ NOTE—A units statement was added editorially as paragraph 1.2 in December 2008.
1. Scope E177 Practice for Use of the Terms Precision and Bias in
ASTM Test Methods
1.1 This practice describes techniques for planning, con-
E178 Practice for Dealing With Outlying Observations
ducting,andanalyzingtheresultsofaninterlaboratorystudyof
a test method. It is designed to be used in conjunction with
3. Significance and Use
Practice C670. Thus, the procedures recommended in this
3.1 Certain criteria need to be met before undertaking an
practice have the limited purpose of providing reliable infor-
interlaboratory study to determine the precision of a test
mation on which precision statements of the type described in
method. It is not necessary that all of the following conditions
Practice C670 can be based. It is not appropriate for use in
described be completely fulfilled in every case; however, if
programs whose purpose is to develop a test method or to
some conditions are not met or are met incompletely, the
assess the relative merits of two or more test methods.
programwillbecomemorecomplicatedandrequiremorework
1.2 Thevaluesstatedininch-poundunitsaretoberegarded
and expense, or may result in impaired information. The
as standard. The values given in parentheses are mathematical
recommendations outlined in this section are intended to
conversions to SI units that are provided for information only
ensurethatthetestmethodisfreeoftechnicaldifficultiestothe
and are not considered standard.
greatest extent possible before an expensive and time-
2. Referenced Documents consuming interlaboratory study is undertaken.
3.1.1 The first requirement is the existence of a valid and
2.1 ASTM Standards:
well-written test method that has been developed in one
C109/C109M Test Method for Compressive Strength of
competent laboratory (or by cooperative work in a small
Hydraulic Cement Mortars (Using 2-in. or [50-mm] Cube
number of laboratories), and has been subjected to a screening
Specimens)
procedure, or to ruggedness testing as described in Practice
C136 Test Method for Sieve Analysis of Fine and Coarse
C1067. As a result of the screening procedure and some
Aggregates
experience with the test method in the sponsoring laboratory
C670 Practice for Preparing Precision and Bias Statements
and one or two others, a written version of the test method has
for Test Methods for Construction Materials
been developed (but not necessarily published as a standard
C1067 Practice for ConductingARuggedness or Screening
method) that describes the test procedure in terms that can
Program for Test Methods for Construction Materials
easily be followed in any properly equipped laboratory. Con-
E105 Practice for Probability Sampling Of Materials
ditions that affect the test results should be identified and the
properdegreeofcontrolofthoseconditionsshouldbespecified
This practice is under the jurisdiction of ASTM Committee C09 on Concrete
in the description of the test procedure (see Note 1).
andConcreteAggregates.ThispracticewasdevelopedjointlybyASTMCommittee
C01, C09, D04, and D18, and is endorsed by all four committees.
NOTE 1—The desired degree of control of conditions that affect test
Current edition approved Dec. 1, 2008. Published February 2009. Originally
resultsmaynotalwaysbepracticallyachievable,andtolerancesinthetest
approvedin1974.Lastpreviouseditionapprovedin2002asC802–96(2002).DOI:
method should recognize this fact. Variations in test results due to
10.1520/C0802-96R08E01.
variations in such conditions contribute to the total variation which
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
determines the precision of the test method. If the resulting variation is so
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
great that uncertainties in average values obtained by the test method are
Standards volume information, refer to the standard’s Document Summary page on
unacceptablyhigh,thenthetestmethoditselfisatfault,andeffortsshould
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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C802–96 (2008)
be made to improve it or to replace it by a better one. An expensive and
difficult ones connected with the process. The number of
time-consuming interlaboratory study should not be undertaken on such a
laboratoriesavailableisseldomasextensiveasonewouldlike,
test method.
and if the test method is new, complicated, or expensive and
3.1.2 Any apparatus required for performing the test should
time-consuming to run, the problem is further complicated.
be appropriately designed and available at reasonable cost. The problem usually becomes one of finding and obtaining the
3.1.3 Personnel in participating laboratories should have
cooperation of enough qualified laboratories to obtain mean-
enough experience with the test method so that they are ingful estimates of precision, rather than that of selection
competent to run the test. The importance of this requirement
among a group of available laboratories. If there is great
will vary with the complexity of the method and the degree to difficulty in obtaining a sufficient number of competent and
which it departs from familiar procedures.
willing laboratories, then the possibility exists that the test
3.1.4 Preliminary knowledge should exist about how method should not be subjected to a formal interlaboratory
changes in materials and conditions affect the test results.
study.
There should be a reasonable degree of certainty that the 4.2 For the purposes of programs using this recommended
within-laboratory variances are the same in different laborato-
practice, it is recommended that at least ten participating
ries, and that troublesome interactions do not exist. These laboratoriesbeincluded (1, 2). Incaseswhereitisimpossible
conditions are investigated in the analysis of the data of an to obtain ten laboratories, the effect of an increased number
interlaboratory study, and are discussed further in 8.2.2, 8.2.3, maybeobtainedbyrepeatingtheprogramwiththesamegroup
and Appendix X1. of laboratories six months later. Usually, results obtained from
3.1.5 Facilities and procedures for procurement, prepara-
the same laboratory after a time lapse of approximately six
tion, and distribution of samples must be available and should months display most of the characteristics of results from a
be as simple and free of difficulties as practicable.
different laboratory, especially if a different operator and
3.1.6 Selectionofsamplesmustbedonebyarandomization apparatus can be used. If this procedure is followed, it is
process, and one person who is familiar with randomization
necessary to be sure that the same materials are used, and that
procedures should be responsible for seeing that the procedure their characteristics have not changed in the interim.
is carried out. Refer to Recommended Practice E105.
4.3 In general, it is recommended that any laboratory that is
3.1.7 Adequate numbers of participating laboratories, op- considered qualified to run the test in routine testing situations
erators,andmaterialsmustbeavailable.Requirementsinthese
should be permitted and encouraged to participate. “Qualified”
areas are specified in Sections 4 and 5. implies proper laboratory facilities and testing equipment,
3.1.8 The entire interlaboratory test program should be
competentoperatorsfamiliarwiththetestmethod,areputation
developed from the beginning with the help and advice of for reliable testing work, and sufficient time and interest to do
persons familiar with statistical procedures and with the
agoodjob.Itdoesnotmean,however,thatonlyaselectgroup
materials involved (see Note 2).The same persons who design oflaboratoriesthatareconsideredtobethosebestqualifiedfor
the experiment should also carry out, or at least have control
the interlaboratory study should be picked. Precision estimates
over, the process of analysis of the data. for inclusion in a test method must be obtained under condi-
tions and through the efforts of laboratories and personnel that
NOTE 2—It may not always be possible to obtain people who are
are representative of the situations in which the test method
familiar with the materials involved who have a sufficient knowledge of
will be used in practice (3). If a laboratory has all the other
the proper statistical techniques and their proper use. In this case, the
committee should obtain the services of a competent statistician who has requirements, but its personnel has had insufficient experience
experienceinpracticalworkwithdatafrommaterialstesting,andprovide
with the method, the operators in that laboratory should be
him with an opportunity for learning something about the particular
givenanopportunitytofamiliarizethemselveswiththemethod
materials and test method involved. Planners of an interlaboratory study
and to practice its application before the interlaboratory study
should also be warned to avoid the pitfall of assuming that the use of a
starts.
large computer necessarily results in special expertise in the handling of
data or the interpretation of results.
5. Materials
3.2 It is important to bear in mind that estimates of the
5.1 The number and type of materials to be included in an
precision of a test method are always based on a particular set
interlaboratory study will depend on the following:
of data obtained at a particular time and they need to be kept
5.1.1 The range of the values of the property being mea-
up-to-date.Asmaterials,apparatus,andconditionschange,and
sured on a given material and how the precision varies over
operators change or gain more experience, the characteristic
that range,
precision of the results obtained may change, especially if the
5.1.2 The number of different materials to which the test
test method is new. In some cases, it may even be desirable to
method is to be applied,
conduct more tests at a later date (though not necessarily a
5.1.3 The difficulty and expense involved in obtaining,
repetition of the complete interlaboratory study) in order to
processing, and distributing samples,
provide a check on estimates previously obtained and either
5.1.4 The difficulty of, length of time required for, and
verify them or introduce revisions.
expense of performing the tests, and
4. Laboratories
4.1 The problem of obtaining competent participating labo-
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
ratories for an interlaboratory study is often one of the most this practice.
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C802–96 (2008)
5.1.5 The uncertainty of prior information on any of these reported. Whenever a test result is defined, either in the test
points. For example, if it is already known that the precision is method or in the instructions to laboratories participating in an
relativelyconstantorproportionaltotheaverageleveloverthe interlaboratory test program, as the average of a particular
range of values of interest, a smaller number of materials will number of determinations, the individual determinations
be needed than if it is known that the precision changes should be reported, in addition to the averages. When two or
erratically at different levels. A preliminary pilot or screening more measurements are averaged to obtain a test result, the
program may help to settle some of these questions, and may data from the interlaboratory test program may be used to
often result in the saving of considerable time and expense in develop an estimate of the precision of these individual
the full interlaboratory study (4). measurements. See 3.3.3 of Practice C670.
5.2 In general, a minimum of three materials should be 7.2.2 Rounding of Data:
considered acceptable.
7.2.2.1 Generally, laboratories should be required to report
all figures obtained in making the measurements, rather than
6. Estimates of Precision
rounding the results before recording them. In some cases, this
6.1 In accordance with Recommended Practice C670, the may result in recording of more digits than is customary or
procedure described in this practice is designed to provide two even more than the test method calls for in the section on
basic estimates of the precision of a test method: (a) single- Reporting(seeX1.3.1).Thisisnecessarybecausethevariation
operator precision, and (b) multilaboratory precision. If other from which information about the precision of the test method
estimates of precision are desired, other references should be comes is contained in the least significant digits, which are
often discarded in reporting the results of routine testing (6).
consulted (see Practice E177) (5).
6.2 Single-operator precision provides an estimate of the For example, Method C136 calls for reporting of percentages
to the nearest whole number. This is adequate for the usual
difference that may be expected between duplicate measure-
mentsmadeonthesamematerialinthesamelaboratorybythe reporting purposes, but for purposes of determining precision,
same operator using the same apparatus within a time span of at least one decimal place is needed. It is better to require the
a few days. reporting of too many decimal places than too few, since a
6.3 Multilaboratory precision provides an estimate of the decisionaboutroundingalldatacanbemadewhentheanalysis
difference that may be expected between measurements made is done. If too few places are reported, however, valuable
on the same material in two different laboratories. informationmaybeirretrievablylost,andtheresultmightwell
be the impairment of the entire program.
7. Collection of Data
7.2.2.2 In cases where a test result is the result of a
7.1 In order to minimize the problems concerned with calculation based on two or more measured quantities, the
analysis of data, a definite form and instructions for obtaining basic measurements should be used in the calculations without
and recording the data should be developed and distributed to anyrounding.Theplannersoftheinterlaboratoryprogramwill
all participating laboratories. thenhavetodeterminehowmanyplacesneedtobereportedin
7.2 Directions to Laboratories—The directions to the labo- order to retain the essentia
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