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    ASTM C670 - 15

    Standard Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials

    Active Standard ASTM C670 | Developed by Subcommittee: C09.94

    Book of Standards Volume: 04.02

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    This practice provides guidance in preparing precision and bias statements for ASTM test methods pertaining to construction materials. Test method shall conform to the maximum acceptable range of individual measurements. In order to be valid the indexes of precision to be included in the precision statement as guides for the operator must be based on estimates of the precision of the test method obtained from a statistically designed inter-laboratory series of tests. This series of tests must involve a sufficient number of laboratories, materials, and replicate measurements so that the results obtained provide reliable estimates of the true precision characteristic of the test method. The procedures described in this practice are based on the assumption that the proper estimates of precision have already been obtained. In any test method, tolerances are placed on the accuracy of measuring equipment. All tests made with a given set of equipment which has an error within the permitted tolerance will produce results with a small consistent bias, but that bias is not inherent in the test method and is not included in the bias statement for the test method. There are two conditions which permit the bias of a test method to be estimated: a standard reference sample of known value has been tested by the test method, and the test method has been applied to a sample which has been compounded in such a manner that the true value of the property being measured is known, such as may be the case, for example, in a test for cement content of concrete.

    This abstract is a brief summary of the referenced standard. It is informational only and not an official part of the standard; the full text of the standard itself must be referred to for its use and application. ASTM does not give any warranty express or implied or make any representation that the contents of this abstract are accurate, complete or up to date.

    1. Scope

    1.1 The Form and Style for ASTM Standards requires that all test methods contain statements on precision and bias. Further, the precision statement is required to contain a statement on single-operator precision (repeatability) and a statement on multilaboratory precision (reproducibility). This practice provides guidance for preparing precision and bias statements that comply with these requirements. Discussion of the purpose and significance of precision and bias statements for users of test methods is also provided. Examples of precision statements that conform to this practice are included in Appendix X1. This practice supplements Practice E177 and has been developed to meet the needs of ASTM Committees dealing with construction materials.

    Note 1: Although this practice is under the jurisdiction of Committee C09, the current version was developed jointly by Committees C01 and C09 and has subsequently been adopted for use by other committees dealing with construction materials.

    1.2 This practice assumes that an interlaboratory study (ILS) has been completed in accordance with Practice C802 or Practice E691. The interlaboratory study provides the necessary statistical values to write the precision and bias statements.

    1.3 The system of units for this practice is not specified. Dimensional quantities in the practice are presented only in examples of precision and bias statements.

    1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

    2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

    ASTM Standards

    C802 Practice for Conducting an Interlaboratory Test Program to Determine the Precision of Test Methods for Construction Materials

    C1067 Practice for Conducting a Ruggedness Evaluation or Screening Program for Test Methods for Construction Materials

    D6607 Practice for Inclusion of Precision Statement Variation in Specification Limits

    E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods

    E456 Terminology Relating to Quality and Statistics

    E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method

    ICS Code

    ICS Number Code 91.100.01 (Construction materials)

    UNSPSC Code

    UNSPSC Code 30000000(Structures and Building and Construction and Manufacturing Components and Supplies)

    Referencing This Standard
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    DOI: 10.1520/C0670-15

    Citation Format

    ASTM C670-15, Standard Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials, ASTM International, West Conshohocken, PA, 2015, www.astm.org

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