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.
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.
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 ( 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 or . 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
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