ASTM E177-90a(1996)

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

SCOPE
1.1 The purpose of this practice is to present concepts necessary to the understanding of the terms "precision" and "bias" as used in quantitative test methods. This practice also describes methods of expressing precision and bias and, in a final section, gives examples of how statements on precision and bias may be written for ASTM test methods.  Note 1-The term "accuracy", used in earlier editions of Practice E177, embraces both precision and bias (see Section 20 and Note 4).
1.2 Informal descriptions of the concepts are introduced in the text as the concepts are developed, and appear in the following sections:  Section Terminology 3 Significance and Use 4 GENERAL CONCEPTS Test Method 5 Measurement Terminology 6 Observation 7 Test Determination 8 Test Result 9 SOURCES OF VARIABILITY Experimental Realization of a Test Method 10 Operator 11 Apparatus 12 Environment 13 Sample 14 Time 15 STATISTICAL CONCEPTS Accepted Reference Value 16 Statistical Control 17 Precision 18 Bias 19 Accuracy 20 Variation of Precision and Bias with Material 21 Variation of Precision and Bias with Sources of Variability 22 COMBINATIONS OF SOURCES OF VARIABILITY Repeatability and Laboratory Bias 23 Other Within-a-Single Laboratory Precisions 24 Reproducibility and Bias of the Test Method 25 Range of Materials 26 METHODS OF EXPRESSING PRECISION AND BIAS Indexes of Precision 27 Preferred Indexes of Precision for ASTM Test Methods 28 Preferred Statements of Bias for ASTM Test Methods 29 Elements of a Statement of Precision and Bias 30 STATEMENTS OF PRECISION AND BIAS Examples of Statements of Precision and Bias 31 APPENDIX Alphabetical List of Descriptions of Terms from the Text XI
1.3 This standard does not purport to address the safety problems 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.

General Information

• Status: Historical
• Publication Date: 31-Dec-1995
• Technical Committee: E11 - Quality and Statistics
• Drafting Committee: E11.20 - Test Method Evaluation and Quality Control

Relations

• Replaced By: ASTM E177-90a(2002) - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 10-Jan-2002

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Contact
ASTM International (www.astm.org) for the latest information.
Designation: E 177 – 90a (Reapproved 1996)
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Practice for
1
Use of the Terms Precision and Bias in ASTM Test Methods
This standard is issued under the fixed designation E 177; 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
Reproducibility and Bias of the Test Method 25
Range of Materials 26
1.1 The purpose of this practice is to present concepts
necessary to the understanding of the terms “precision” and
METHODS OF EXPRESSING PRECISION AND BIAS
“bias” as used in quantitative test methods. This practice also
Indexes of Precision 27
describes methods of expressing precision and bias and, in a
Preferred Indexes of Precision for ASTM Test Methods 28
final section, gives examples of how statements on precision Preferred Statements of Bias for ASTM Test Methods 29
Elements of a Statement of Precision and Bias 30
and bias may be written for ASTM test methods.
STATEMENTS OF PRECISION AND BIAS
NOTE 1—The term “accuracy”, used in earlier editions of Practice
E 177, embraces both precision and bias (see Section 20 and Note 4).
Examples of Statements of Precision and Bias 31
1.2 Informal descriptions of the concepts are introduced in
APPENDIX
the text as the concepts are developed, and appear in the
following sections:
Alphabetical List of Descriptions of Terms from the Text Appendix
X1
Section
Terminology 3
1.3 This standard does not purport to address all of the
Significance and Use 4
safety concerns, if any, associated with its use. It is the
GENERAL CONCEPTS
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
Test Method 5
bility of regulatory limitations prior to use.
Measurement Terminology 6
Observation 7
Test Determination 8
2. Referenced Documents
Test Result 9
2.1 ASTM Standards:
2
SOURCES OF VARIABILITY
E 178 Practice for Dealing with Outlying Observations
2
E 456 Terminology Relating to Quality and Statistics
Experimental Realization of a Test Method 10
Operator 11 E 691 Practice for Conducting an Interlaboratory Study to
2
Apparatus 12
Determine the Precision of a Test Method
Environment 13
2
E 1169 Guide for Conducting Ruggedness Tests
Sample 14
2.2 ANSI/ASQC Standard:
Time 15
A1-1978 Definitions, Symbols, Formulas and Tables for
STATISTICAL CONCEPTS
3
Control Charts
2.3 Other Documents:
Accepted Reference Value 16
Statistical Control 17
TAPPI Collaborative Reference Program, Reports
Precision 18
4
25 through 51, Aug. 1973 through Jan. 1978
Bias 19
3
Accuracy 20 ASQC Glossary and Tables for Statistical Quality Control
Variation of Precision and Bias with Material 21
Variation of Precision and Bias with Sources of Variability 22
3. Terminology
COMBINATIONS OF SOURCES OF VARIABILITY 3.1 The terminology defined in Terminology E 456 applies
in all areas affected by this practice, except where modified by
Repeatability and Laboratory Bias 23
this practice.
Other Within-a-Single Laboratory Precisions 24
1 2
This practice is under the jurisdiction of ASTM Committee E-11 on Quality and Annual Book of ASTM Standards, Vol 14.02.
3
Statistics and is the direct responsibility of Subcommittee E11.20on Test Method Available from American Society for Quality Control, 230 West Wells St.,
Evaluation and Quality Control. Milwaukee, WI 53203.
4
Current edition approved June 29, 1990. Published August 1990. Originally Available from the Technical Association of the Pulp and Paper Industry,
published as E 177 – 61. Last previous edition E 177 – 90. Technology Park/Atlanta, P.O. Box 105113, Atlanta, GA 30348.
1

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NOTICE:¬This¬standard¬has¬either¬been¬superceded¬and¬replaced¬by¬a¬new¬version¬or¬discontinued.¬
Contact¬ASTM¬International¬(www.astm.org)¬for¬the¬latest¬information.¬
E 177
temperature would be introduced to establish the limits of significant
3.2 This practice is specifically concerned with the devel-
5
effect, (1, 2, 3).
opment of statements on precision and bias for inclusion as
descriptors of the performance of a test method. This applica- 5.4 A well-written test method specifies control over such
tion requires refinement of the Terminology E 456 definitions,
factors as the test equipment, the test environment, the quali-
as discussed herein. fications of the operator (explicitly or implicitly), the prepara-
tion of test specimens, and the operating procedure for using
3.3 The informal descriptions of concepts deve
...