ASTM D2777-12
(Practice)Standard Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
Standard Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
SIGNIFICANCE AND USE
Following this practice should result in precision-and-bias statements that can be achieved by any laboratory properly using the test method studied. These precision-and-bias statements provide the basis for generic limits for use in the Quality Control section of the test method. Optionally, the detection and quantitation values provide estimates of the level at which most laboratories should be able to achieve confident detection and meet the minimum precision (expressed as relative standard deviation) expected.
The method specifies the matrices for which the test method is appropriate. The collaborative test corroborates the write-up within the limitations of the test design. An extensive test can only use representative matrices so that universal applicability cannot be implied from the results.
The fundamental assumption of the collaborative study is that the matrices tested, the concentrations tested, and the participating laboratories are a representative and fair evaluation of the scope and applicability of the test method as written.
SCOPE
1.1 This practice establishes uniform standards for estimating and expressing the precision and bias of applicable test methods for Committee D19 on Water. In principle, all test methods are covered by this practice.
1.2 Except as specified in 1.4, 1.5, and 1.6, this practice requires the task group proposing a new test method to carry out a collaborative study from which statements for precision (overall and single-operator standard-deviation estimates) and bias can be developed. This practice provides general guidance to task groups in planning and conducting such determinations of precision and bias.
1.3 This practice also provides guidance to task groups for conducting limited-scale collaborative studies (known as “comparability studies”) for test methods that have been revised, when such revision includes substantive modifications. Examples of substantive modifications may include, but are not limited to, changes in mandatory or allowable instrumentation, reagents, reaction times, etc.
1.3.1 Changes to applicable water matrices in the Scope of a method may constitute a substantive modification under this provision. However, recognize that even the original collaborative study may not have used all the various matrix types specified in the method’s original Scope.
1.3.2 A method's concentration-range extension that is deemed to merit additional collaborative testing (even without a method modification that would otherwise be considered substantive) shall require a full collaborative study, as described in Sections 7.1-7.5, but only at Youden-pair concentrations representative of the extended range. Note that such a collaborative study could involve as little as a single-sample Youden-pair study in a single reproducible matrix.
1.3.3 Whether a revision to a test method includes substantive modification shall be determined by consensus of the Committee.
1.4 If a full-scale collaborative study is not technically feasible, due to the nature of the test method or instability of samples, the largest feasible scaled-down collaborative study shall be conducted to provide the best possible limited basis for estimating the overall and single-operator standard deviations.
1.4.1 Examples of acceptable scaled-down studies are the local-area studies conducted by Subcommittee D19.24 on microbiological methods because of inherent sample instability. These studies involve six or more completely independent local-area analysts who can begin analysis of uniform samples at an agreed upon time.
1.4.2 If uniform samples are not feasible under any circumstances, a statement of single-operator precision will meet the requirements of this practice. Whenever possible, this statement should be developed from data generated by independent multiple operators, each doing replicate analyses on independent samples (of a specific matrix type), which gener...
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Designation: D2777 − 12
StandardPractice for
Determination of Precision and Bias of Applicable Test
1
Methods of Committee D19 on Water
This standard is issued under the fixed designation D2777; 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 1.4 If a full-scale collaborative study is not technically
feasible, due to the nature of the test method or instability of
1.1 This practice establishes uniform standards for estimat-
samples, the largest feasible scaled-down collaborative study
ing and expressing the precision and bias of applicable test
shallbeconductedtoprovidethebestpossiblelimitedbasisfor
methods for Committee D19 on Water. In principle, all test
estimating the overall and single-operator standard deviations.
methods are covered by this practice.
1.4.1 Examples of acceptable scaled-down studies are the
1.2 Except as specified in 1.4, 1.5, and 1.6, this practice
local-area studies conducted by Subcommittee D19.24 on
requires the task group proposing a new test method to carry
microbiological methods because of inherent sample instabil-
out a collaborative study from which statements for precision
ity. These studies involve six or more completely independent
(overall and single-operator standard-deviation estimates) and
local-area analysts who can begin analysis of uniform samples
bias can be developed.This practice provides general guidance
at an agreed upon time.
to task groups in planning and conducting such determinations
1.4.2 If uniform samples are not feasible under any
of precision and bias.
circumstances, a statement of single-operator precision will
meet the requirements of this practice.Whenever possible, this
1.3 This practice also provides guidance to task groups for
conducting limited-scale collaborative studies (known as statement should be developed from data generated by inde-
pendent multiple operators, each doing replicate analyses on
“comparability studies”) for test methods that have been
revised,whensuchrevisionincludessubstantivemodifications. independent samples (of a specific matrix type), which gener-
ally fall within specified concentration ranges (see 7.2.5.2 (3)).
Examplesofsubstantivemodificationsmayinclude,butarenot
limited to, changes in mandatory or allowable instrumentation, 1.4.3 This practice is not applicable to methodology involv-
ing continuous sampling or continuous measurement, or both,
reagents, reaction times, etc.
1.3.1 Changes to applicable water matrices in the Scope of of specific constituents and properties.
a method may constitute a substantive modification under this 1.4.4 This practice is also not applicable to open-channel
flow measurements.
provision. However, recognize that even the original collab-
orative study may not have used all the various matrix types
1.5 A collaborative study that satisfied the requirements of
specified in the method’s original Scope.
the version of this practice in force when the study was
1.3.2 A method’s concentration-range extension that is
conducted will continue to be considered an adequate basis for
deemed to merit additional collaborative testing (even without
the precision-and-bias statement required in each test method.
a method modification that would otherwise be considered
If the study does not satisfy the current minimum requirements
substantive) shall require a full collaborative study, as de-
for a collaborative study, a statement listing the study’s
scribed in Sections 7.1-7.5, but only at Youden-pair concen-
deficiencies and a reference to this paragraph shall be included
trations representative of the extended range. Note that such a
in the precision-and-bias statement as the basis for an exemp-
collaborative study could involve as little as a single-sample
tion from the current requirements.
Youden-pair study in a single reproducible matrix.
1.6 This paragraph relates to special exemptions not clearly
1.3.3 Whether a revision to a test method includes substan-
acceptable under 1.4 or 1.5. With the approval of Committee
tive modification shall be determined by consensus of the
D19 on the recommendation of the Results Advisor and the
Committee.
Technical Operations Section of the Executive Subcommittee
of Committee D19, a statement giving a compelling reason
why compliance with all or specific points of this practice
1
This practice is under the jurisdiction ofASTM Committee D19 on Water and
2
cannot be achieved will meet both ASTM requirements (1)
is the direct responsibility of Subcommittee D19.02 on Quality Systems,
Specification, and Statistics.
Current edition approved June 15, 2012. Published
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