Standard Practice for DETERMINATION OF PRECISION AND BIAS OF APPLICABLE METHODS OF COMMITTEE D-19 ON WATER
|Publication Date:||29 August 1986|
This practice establishes uniform standards for expressing the precision and bias of applicable test methods for Committee D-19 on Water.
Except as specified in 1,3. 1.4. 1.5. and 1.6. this practice requires that the task group proposing a new test method must carry out a collaborative study from which statements for precision (multiple laboratory operational and single-operator standard deviation estimates) and observed bias can be developed. This practice provides general guidance to task groups in planning and conducting such determinations of precision and bias.
Where. due to the nature of the test or instability of the sample. a full-scale collaborative test is not technically feasible. a statement of single-operator precision (Section 10) will meet the requirements of this practice. Whenever possible. this statement should be developed from data generated by multiple operators. each doing replicate analyses on independent samples which generally fall within specified concentration ranges, This practice is not applicable to methodology involving continuous sampling and measurement of specific constituents and properties.
Many of the test methods adopted prior to 1980 do not have adequate precision and bias statements. and there is insufficient information to satisfactorily improve the statements. These test methods are being used. and it is generally agreed that they should be continued as standards until 1985. while a proper collaborative study is conducted. In the interim. a warning must be placed in the scope and precision sections to alert the user that there has not been adequate collaborative testing to validate the test method.
Existing test methods that do have adequate precision and bias statements based on a minimum of three laboratories for a total of six operators do not require further collaborative testing. and such deficiencies must be listed in the precision and bias statements.
With the recommendation of the Results Advisor and the concurrence of the Technical Operations Section of the Executive Subcommittee. a statement giving a compelling reason why all or specific points of this practice cannot be fully complied with will meet both ASTM requirements (1)2 and the related requirements of this practice.
In principle. all test methods are covered by this practice.
In Section II. this practice shows exemplary precision and bias statement formats for: (I) test methods yielding a numerical measure. (2) test methods yielding a nonnumerical report of success or failure based on criteria specified in the procedure. and (3) test methods specifying that procedures in another ASTM method are to be used with only insignificant modifications.
2 The boldface numbers in parentheses refer 10 the list of references at the end of this practice.