ASTM D2777-08
(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.
1.2 Except as specified in 1.3, 1.4, and 1.5, 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 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.
1.3.1 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.
1.3.2 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 generally fall within specified concentration ranges (see 7.2.5.2 (3)).
1.3.3 This practice is not applicable to methodology involving continuous sampling or continuous measurement, or both, of specific constituents and properties.
1.3.4 This practice is also not applicable to open-channel flow measurements.
1.4 A collaborative study that satisfied the requirements of the version of this practice in force when the study was conducted will continue to be considered an adequate basis for the precision-and-bias statement required in each test method. If the study does not satisfy the current minimum requirements for a collaborative study, a statement listing the study's deficiencies and a reference to this paragraph shall be included in the precision-and-bias statement as the basis for an exemption from the current requirements.
1.5 This paragraph relates to special exemptions not clearly acceptable under 1.3 or 1.4. With the approval of Committee D19 on the recommendation of the Results Advisor and the 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 cannot be achieved will meet both ASTM requirements (1) and the related requirements of this practice. In addition, Committee D19, through a Main Commi...
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Designation:D2777–08
Standard Practice for
Determination of Precision and Bias ofApplicable Test
1
Methods of Committee D19 on Water
This standard is issued under the fixed designation D 2777; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope conducted will continue to be considered an adequate basis for
the precision-and-bias statement required in each test method.
1.1 This practice establishes uniform standards for estimat-
If the study does not satisfy the current minimum requirements
ing and expressing the precision and bias of applicable test
for a collaborative study, a statement listing the study’s
methods for Committee D19 on Water.
deficiencies and a reference to this paragraph shall be included
1.2 Except as specified in 1.3, 1.4, and 1.5, this practice
in the precision-and-bias statement as the basis for an exemp-
requires the task group proposing a new test method to carry
tion from the current requirements.
out a collaborative study from which statements for precision
1.5 This paragraph relates to special exemptions not clearly
(overall and single-operator standard-deviation estimates) and
acceptable under 1.3 or 1.4. With the approval of Committee
bias can be developed.This practice provides general guidance
D19 on the recommendation of the Results Advisor and the
to task groups in planning and conducting such determinations
Technical Operations Section of the Executive Subcommittee
of precision and bias.
of Committee D19, a statement giving a compelling reason
1.3 If a full-scale collaborative study is not technically
why compliance with all or specific points of this practice
feasible, due to the nature of the test method or instability of
2
cannot be achieved will meet both ASTM requirements (1)
samples, the largest feasible scaled-down collaborative study
and the related requirements of this practice. In addition,
shallbeconductedtoprovidethebestpossiblelimitedbasisfor
Committee D19, through a Main Committee ballot, may
estimating the overall and single-operator standard deviations.
approve publication of a “Preliminary” Standard Method for a
1.3.1 Examples of acceptable scaled-down studies are the
period not to exceed 5 years. Preliminary Standards must
local-area studies conducted by Subcommittee D19.24 on
contain a minimum of a single-operator precision-and-bias
microbiological methods because of inherent sample instabil-
statement and a Quality Control section based on the single
ity. These studies involve six or more completely independent
operator data. Publication of a Preliminary Standard is condi-
local-area analysts who can begin analysis of uniform samples
tional on the approval of a full D 2777 collaborative study
at an agreed upon time.
design for the standard. Precision-and-bias statements autho-
1.3.2 If uniform samples are not feasible under any circum-
rized by this paragraph shall include the date of approval by
stances, a statement of single-operator precision will meet the
Committee D19.
requirements of this practice. Whenever possible, this state-
1.6 In principle, all test methods are covered by this
ment should be developed from data generated by independent
practice.
multiple operators, each doing replicate analyses on indepen-
1.7 In Section 12 this practice shows exemplary precision-
dent samples (of a specific matrix type), which generally fall
and-bias-statement formats for: (1) test methods yielding a
within specified concentration ranges (see 7.2.5.2 (3)).
numerical measure, (2) test methods yielding a non-numerical
1.3.3 This practice is not applicable to methodology involv-
report of success or failure based on criteria specified in the
ing continuous sampling or continuous measurement, or both,
procedure, and (3) test methods specifying that procedures in
of specific constituents and properties.
another ASTM test method are to be used with only insignifi-
1.3.4 This practice is also not applicable to open-channel
cant modifications.
flow measurements.
1.8 All studies, even those exempt from some requirements
1.4 A collaborative study that satisfied the requirements of
under 1.3 or 1.5, shall receive approval from the Results
the version of this practice in force when the study was
Advisor before being conducted (see Section 8) and after
completion (see Section 13).
1
This practice is under the jurisdiction ofASTM Committee D19 on Water and
is the direct responsibility of Subcommittee D19.02 on Quality Systems, Specifi-
cation, and Statistics.
2
Current edition approved Jan. 15, 2008. Published February 2008. Originally The boldface numbers in parenthese
...
This document is not anASTM standard and is intended only to provide the user of anASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation:D2777–06 Designation:D2777–08
Standard Practice for
Determination of Precision and Bias ofApplicable Test
1
Methods of Committee D19 on Water
This standard is issued under the fixed designation D 2777; 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 (e) indicates an editorial change since the last revision or reapproval.
1. 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.
1.2 Except as specified in 1.3, 1.4, and 1.5, 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.Thispracticeprovidesgeneralguidancetotaskgroupsinplanningandconductingsuchdeterminationsofprecisionand
bias.
1.3 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.
1.3.1 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.
1.3.2 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 generally fall within specified
concentration ranges (see 7.2.5.2 ( 3)).
1.3.3 This practice is not applicable to methodology involving continuous sampling or continuous measurement, or both, of
specific constituents and properties.
1.3.4 This practice is also not applicable to open-channel flow measurements.
1.4 A collaborative study that satisfied the requirements of the version of this practice in force when the study was conducted
willcontinuetobeconsideredanadequatebasisfortheprecision-and-biasstatementrequiredineachtestmethod.Ifthestudydoes
not satisfy the current minimum requirements for a collaborative study, a statement listing the study’s deficiencies and a reference
to this paragraph shall be included in the precision-and-bias statement as the basis for an exemption from the current requirements.
1.5 This paragraph relates to special exemptions not clearly acceptable under 1.3 or 1.4. With the approval of Committee D19
ontherecommendationoftheResultsAdvisorandtheTechnicalOperationsSectionoftheExecutiveSubcommitteeofCommittee
D19, a statement giving a compelling reason why compliance with all or specific points of this practice cannot be achieved will
2
meet both ASTM requirements (1) and the related requirements of this practice. In addition, Committee D19, through a Main
Committee ballot, may approve publication of a “Preliminary” Standard Method for a period not to exceed 5 years. Preliminary
Standards must contain a minimum of a single-operator precision-and-bias statement and a Quality Control section based on the
single operator data. Publication of a Preliminary Standard is conditional on the approval of a full D 2777 collaborative study
designforthestandard.Precision-and-biasstatementsauthorizedbythisparagraphshallincludethedateofapprovalbyCommittee
D19.
1.6 In principle, all test methods are covered by this practice.
1.7 InSection12thispracticeshowsexemplaryprecision-and-bias-statementformatsfor:(1)testmethodsyieldinganumerical
measure, (2) test methods yielding a non-numerical report of success or failure based on criteria specified in the procedure, and
(3) test methods specifying that procedures in another ASTM test method are to be used with only insignificant modifications.
1.8 All studies, even those exempt from some requirements under 1.3 or 1.5, shall receive approval from the Results Advisor
before being conducted (see Section 8) and after completion (see Section 13).
1
This practice is under the jurisdiction ofASTM Committee D19 on Water and is the direct
...
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