ASTM C1215-92(2006)
(Guide)Standard Guide for Preparing and Interpreting Precision and Bias Statements in Test Method Standards Used in the Nuclear Industry
Standard Guide for Preparing and Interpreting Precision and Bias Statements in Test Method Standards Used in the Nuclear Industry
SCOPE
1.1 This guide covers terminology useful for the preparation and interpretation of precision and bias statements.
1.2 In formulating precision and bias statements, it is important to understand the statistical concepts involved and to identify the major sources of variation that affect results. Appendix X1 provides a brief summary of these concepts.
1.3 To illustrate the statistical concepts and to demonstrate some sources of variation, a hypothetical data set has been analyzed in Appendix X2. Reference to this example is made throughout this guide.
1.4 It is difficult and at times impossible to ship nuclear materials for interlaboratory testing. Thus, precision statements for test methods relating to nuclear materials will ordinarily reflect only within-laboratory variation.
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Standards Content (Sample)
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Designation:C1215–92 (Reapproved 2006)
Standard Guide for
Preparing and Interpreting Precision and Bias Statements in
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Test Method Standards Used in the Nuclear Industry
This standard is issued under the fixed designation C1215; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
Test method standards are required to contain precision and bias statements. This guide contains a
glossary that explains various terms that often appear in these statements as well as an example
illustrating such statements for a specific set of data. Precision and bias statements are shown to vary
according to the conditions under which the data were collected.This guide emphasizes that the error
model (an algebraic expression that describes how the various sources of variation affect the
measurement) is an important consideration in the formation of precision and bias statements.
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1. Scope Nuclear Materials Management
1.1 Thisguidecoversterminologyusefulforthepreparation
3. Terminology for Precision and Bias Statements
and interpretation of precision and bias statements.
3.1 Definitions:
1.2 In formulating precision and bias statements, it is
3.1.1 accuracy (see bias)—(1) bias. (2) the closeness of a
importanttounderstandthestatisticalconceptsinvolvedandto
measured value to the true value. (3) the closeness of a
identify the major sources of variation that affect results.
measured value to an accepted reference or standard value.
Appendix X1 provides a brief summary of these concepts.
3.1.1.1 Discussion—For many investigators, accuracy is
1.3 To illustrate the statistical concepts and to demonstrate
attained only if a procedure is both precise and unbiased (see
some sources of variation, a hypothetical data set has been
bias). Because this blending of precision into accuracy can
analyzed in Appendix X2. Reference to this example is made
resultoccasionallyinincorrectanalysesandunclearstatements
throughout this guide.
of results, ASTM requires statement on bias instead of accu-
1.4 It is difficult and at times impossible to ship nuclear
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racy.
materialsforinterlaboratorytesting.Thus,precisionstatements
3.1.2 analysis of variance (ANOVA)—thebodyofstatistical
for test methods relating to nuclear materials will ordinarily
theory,methods,andpracticesinwhichthevariationinasetof
reflect only within-laboratory variation.
data is partitioned into identifiable sources of variation.
2. Referenced Documents Sources of variation may include analysts, instruments,
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samples, and laboratories. To use the analysis of variance, the
2.1 ASTM Standards:
data collection method must be carefully designed based on a
E177 Practice for Use of the Terms Precision and Bias in
modelthatincludesallthesourcesofvariationofinterest.(See
ASTM Test Methods
Example, X2.1.1)
E691 Practice for Conducting an Interlaboratory Study to
3.1.3 bias (see accuracy)—a constant positive or negative
Determine the Precision of a Test Method
deviation of the method average from the correct value or
2.2 ANSI Standard:
accepted reference value.
ANSI N15.5 Statistical Terminology and Notation for
3.1.3.1 Discussion—Bias represents a constant error as
opposed to a random error.
(a) A method bias can be estimated by the difference (or
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This guide is under the jurisdiction ofASTM Committee C26 on Nuclear Fuel
relative difference) between a measured average and an ac-
Cycle and is the direct responsibility of Subcommittee C26.08 on Quality Assur-
cepted standard or reference value. The data from which the
ance, Statistical Applications, and Reference Materials.
Current edition approved Jan. 1, 2006. Published February 2006. Originally estimateisobtainedshouldbestatisticallyanalyzedtoestablish
approvedin1992.Lastpreviouseditionapprovedin1997asC1215–92(1997).DOI:
10.1520/C1215-92R06.
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For referenced ASTM standards, visit the ASTM website, www.astm.org, or
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contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
Standards volume information, refer to the standard’s Document Summary page on 4th Floor, New York, NY 10036, http://www.ansi.org.
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the ASTM website. Refer to Form and Style for ASTM Standards, 8th Ed., 1989, ASTM.
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Please contact ASTM International (www.astm.org) for the latest information.
C1215
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