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ASTM E3264-21

(Guide)

Standard Guide for Homogeneity of Samples and Reference Materials Used for Inter- and Intra-Laboratory Studies

Standard Guide for Homogeneity of Samples and Reference Materials Used for Inter- and Intra-Laboratory Studies

SIGNIFICANCE AND USE
5.1 This guide presents techniques and guidance for evaluating and assuring homogeneity of individual samples or bulk materials and can be used for either interlaboratory or intra-laboratory studies. The types of studies include, but are not limited to, studies to determine precision estimates for test methods, proficiency testing programs, and studies related to quality control of testing within a single laboratory.  
5.2 Because the test results of any laboratory study are affected by the quality of the samples tested, producing homogeneous samples and determining the degree of homogeneity is important for interpreting the results of the study.  
5.3 Five techniques are presented in this guide to evaluate sample homogeneity for a range of circumstances and degrees of rigor. The circumstances under which the studies are conducted and the degree of rigor required may differ. The user should consider the circumstances listed in each technique to determine which is appropriate for the study at hand.  
5.4 Each of the Techniques 1, 2, and 3 provides a procedure for testing and evaluating sample homogeneity when replicate testing of the samples is possible. Technique 4 provides a plan to evaluate sample homogeneity when replicate testing is not possible. Technique 5 recommends practices for producing homogeneous samples for circumstances when homogeneity testing is not possible.  
5.5 When the conditions of adequate within-sample homogeneity and between-sample homogeneity are satisfied, any differences in test results on multiple samples can reasonably be attributed to testing variation and not due to sample variation.  
5.6 When differences within or between samples are discovered and the samples are deemed insufficiently homogeneous, the sample preparation process can be improved or corrected and a new set of samples can be prepared. Or, in cases where the sample homogeneity cannot be improved or for other reasons when the samples must be used, the method of eval...
SCOPE
1.1 This guide presents techniques and guidance for evaluating and assuring homogeneity of individual samples and bulk materials used for interlaboratory and intra-laboratory studies.  
1.2 This guide is applicable to samples and reference materials used for proficiency testing programs and for interlaboratory studies to determine precision estimates for test methods. It may also be useful for activities related to quality control of testing within a single laboratory.  
1.3 Five techniques are presented for assessing sample homogeneity. The five techniques are not an exhaustive list of available techniques for assessing homogeneity of samples, but the techniques were chosen to cover a range of circumstances (and various degrees of rigor required) for laboratory studies of various types and purposes.  
1.4 Each of the first four techniques provides a scheme for testing for homogeneity and a statistical procedure for evaluating the results of the homogeneity testing. The circumstances are described for which each of the techniques is suited.  
1.5 For circumstances when homogeneity testing is not possible, the fifth technique provides guidance for producing homogeneous samples.  
1.6 The appendixes of this guide provide example spreadsheets for Techniques 1, 2, 3, and 4.  
1.7 This guide is not intended for evaluation of certified reference materials (CRMs) or materials used for calibration.  
1.8 Units—The system of units for this standard is not specified. Dimensional quantities in the standard are presented only as illustrations of calculation methods. The examples are not binding on products or test methods treated.  
1.9 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, health, and environmental practices and determine the applicability of regulatory limitations prior to ...

General Information

Status
Published
Publication Date
31-Mar-2021
ICS
19.020 - Test conditions and procedures in general
Technical Committee
E11 - Quality and Statistics
Drafting Committee
E11.20 - Test Method Evaluation and Quality Control
Current Stage
Ref Project

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ASTM E3264-21 - Standard Guide for Homogeneity of Samples and Reference Materials Used for Inter- and Intra-Laboratory StudiesASTM E3264-21 - Standard Guide for Homogeneity of Samples and Reference Materials Used for Inter- and Intra-Laboratory Studies
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ASTM E3264-21 - Standard Guide for Homogeneity of Samples and Reference Materials Used for Inter- and Intra-Laboratory Studies
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This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E3264 − 21 An American National Standard
Standard Guide for
Homogeneity of Samples and Reference Materials Used for
1
Inter- and Intra-Laboratory Studies
This standard is issued under the fixed designation E3264; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
1.1 This guide presents techniques and guidance for evalu-
1.10 This international standard was developed in accor-
ating and assuring homogeneity of individual samples and bulk
dance with internationally recognized principles on standard-
materials used for interlaboratory and intra-laboratory studies.
ization established in the Decision on Principles for the
1.2 This guide is applicable to samples and reference
Development of International Standards, Guides and Recom-
materials used for proficiency testing programs and for inter-
mendations issued by the World Trade Organization Technical
laboratory studies to determine precision estimates for test
Barriers to Trade (TBT) Committee.
methods. It may also be useful for activities related to quality
2. Referenced Documents
control of testing within a single laboratory.
2
2.1 ASTM Standards:
1.3 Five techniques are presented for assessing sample
C33/C33M Specification for Concrete Aggregates
homogeneity. The five techniques are not an exhaustive list of
C1128 Guide for Preparation of Working Reference Materi-
available techniques for assessing homogeneity of samples, but
als for Use in Analysis of Nuclear Fuel Cycle Materials
the techniques were chosen to cover a range of circumstances
D5956 Guide for Sampling Strategies for Heterogeneous
(and various degrees of rigor required) for laboratory studies of
Wastes
various types and purposes.
D6299 Practice for Applying Statistical Quality Assurance
1.4 Each of the first four techniques provides a scheme for
and Control Charting Techniques to Evaluate Analytical
testing for homogeneity and a statistical procedure for evalu-
Measurement System Performance
ating the results of the homogeneity testing. The circumstances
D7915 Practice for Application of Generalized Extreme
are described for which each of the techniques is suited.
Studentized Deviate (GESD) Technique to Simultane-
1.5 For circumstances when homogeneity testing is not ously Identify Multiple Outliers in a Data Set
possible, the fifth technique provides guidance for producing
E105 Guide for Probability Sampling of Materials
homogeneous samples. E178 Practice for Dealing With Outlying Observations
E456 Terminology Relating to Quality and Statistics
1.6 The appendixes of this guide provide example spread-
E691 Practice for Conducting an Interlaboratory Study to
sheets for Techniques 1, 2, 3, and 4.
Determine the Precision of a Test Method
1.7 This guide is not intended for evaluation of certified
E1402 Guide for Sampling Design
reference materials (CRMs) or materials used for calibration.
E2282 Guide for Defining the Test Result of a Test Method
3
2.2 ISO Standards:
1.8 Units—The system of units for this standard is not
ISO Guide 30 Reference Materials – Selected Terms and
specified. Dimensional quantities in the standard are presented
Definitions
only as illustrations of calculation methods. The examples are
ISO 13528 Statistical Methods for Use in Proficiency Test-
not binding on products or test methods treated.
ing by Interlaboratory Comparison
1.9 This standard does not purport to address all of the
ISO 3534 Statistics Vocabulary and Symbols – Part 2 Ap-
safety concerns, if any, associated with its use. It is the
plied Statistics
responsibility of the user of this standard to establish appro-
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
1
This guide is under the jurisdiction of ASTM Committee E11 on Quality and Standards volume information, refer to the standard’s Document Summary page on
Statistics and is the direct responsibility of Subcommittee E11.20 on Test Method the ASTM website.
3
Evaluation and Quality Control. Available from International Organization for Standardization (ISO), ISO
Current edition approved April 1, 2021. Published January 2022. DOI: 10.1520/ Central Secretariat, Chemin de Blandonnet 8, CP 401, 1214 Vernier, Geneva,
E3264-21. Switzerland, https://www.iso.org.
Copyright
...

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This guide identifies statistical procedures for use in developing new test methods or revising or evaluating existing test methods, or both. It also cites statistical procedures especially useful in the application of test methods. This standard recommends what approaches may be taken and indicates which standards may be used to perform such assessments.
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FIG. 1 Sequence of Steps  
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This practice describes the techniques for planning, conducting, analyzing, and treating the results of an interlaboratory study (ILS) of a test method. The statistical techniques described in this practice provide adequate information for formulating the precision statement of a test method. This practice is also concerned exclusively with test methods which yield a single numerical figure as the test result, although the single figure may be the outcome of a calculation from a set of measurements. ASTM regulations require precision statements in all test methods in terms of repeatability and reproducibility and knowledge of the test method precision is useful in commerce and in technical work when comparing test results against standard values or between data sources.
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4.1.1 When a test method is applied to a large number of portions of a material that are as nearly alike as possible, the test results obtained will not all have the same value. A measure of the degree of agreement among these test results describes the precision of the test method for that material. Numerical measures of the variability between such test results provide inverse measures of the precision of the test method. Greater variability implies smaller (that is, poorer) precision and larger imprecision.  
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ABSTRACT
The purpose of this guide is to provide guidelines for identifying the elements that comprise the test result of a test method and to illustrate how these elements combine into the test result. It covers the types of measurement scales used for expressing observations and test results. This guide provides information on the construction of test results from more elemental measurements.
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SCOPE
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5.1 This practice is suitable for the determination of extractable substances that may be found in materials used in systems or components requiring a high level of cleanliness, such as oxygen systems. Soft goods, such as seals and valve seats, may be tested as received. Gloves and wipes, or samples thereof, to be used in cleaning operations may be evaluated prior to use to ensure that the proposed extracting agent does not extract or deposit chemicals, or both, on the surface to be cleaned.  
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SCOPE
1.1 This practice may be used to extract nonvolatile and semivolatile residues from materials such as new and used gloves, new and used wipes, component soft goods, and so forth. When used with proposed cleaning materials (wipes, gloves, and so forth), this practice may be used to determine the potential of the proposed solvent or other fluids to extract contaminants (plasticizers, residual detergents, brighteners, and so forth) and deposit them on the surface being cleaned.  
1.2 This practice is not suitable for the evaluation of particulate contamination.  
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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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
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ASTM D6259-23(Practice)
Standard Practice for Determination of a Pooled Limit of Quantitation for a Test Method

SIGNIFICANCE AND USE
5.1 Background—In a single laboratory, the limit of quantitation, LOQ, equal to ten times the standard deviation obtained under repeatability conditions extrapolated to zero concentration (s0) based on samples with close to zero concentrations has been recommended.3 A test result at this LOQ has an uncertainty of ±30 % at the 99 % confidence level.  
5.1.1 This practice uses a regression technique to determine a similar limit for a test method (PLOQ) using statistically pooled repeatability standard deviations over multiple operators/laboratories/samples from ILS data. This PLOQ can be used by industry to assess the reliability of a test method, or, compare reliability of different test methods, for quantitative measurement at concentrations near zero. Similarly, quantitative test results obtained using the test method for levels at or below the PLOQ can be expected by industry to have an uncertainty of ±30 % or greater at the 95 % confidence level.  
5.1.2 The regression technique described in this practice can also be used to determine a limit of quantitation specific for a single laboratory (LLOQ). The limit thus quantified for one laboratory is defined by this standard as the laboratory limit of quantitation (LLOQ).  
5.1.3 It should be noted that since differences in repeatability testing capabilities between different laboratories can exist, therefore, LLOQ determined at a single laboratory can be different than the PLOQ determined for the test method.  
5.2 Values below the PLOQ are deemed by this practice to be too uncertain for meaningful use in commerce, or in regulatory activities.
SCOPE
1.1 This practice covers the use of standard regression techniques and data from an interlaboratory study to determine a lower quantitative limit for a test method. This determined lower limit represents the numerical limit at or above which the test results are considered to be quantitatively meaningful for commerce or regulatory activities by this practice. It is defined by this standard as the pooled limit of quantitation (PLOQ) for the test method.  
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ABSTRACT
This guide identifies statistical procedures for use in developing new test methods or revising or evaluating existing test methods, or both. It also cites statistical procedures especially useful in the application of test methods. This standard recommends what approaches may be taken and indicates which standards may be used to perform such assessments.
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4.1 The creation of a standardized test method generally follows a series of steps from inception to approval and ongoing use. In all such stages there are questions of how well the test method performs.  
4.1.1 Assessments of a new or existing test method generally involve statistical planning and analysis. This standard recommends what approaches may be taken and indicates which standards may be used to perform such assessments.  
4.2 This standard introduces a series of phases which are recommended to be considered during the life cycle of a test method as depicted in Fig. 1. These begin with a design phase where the standard is initially prepared. A development phase involves a variety of experiments that allow further refinement and understanding of how the test method performs within a laboratory. In an evaluation phase the test method is then examined by way of interlaboratory studies resulting in precision and bias statistics which are published in the standard. Finally, the test method is subject to a monitoring phase.
FIG. 1 Sequence of Steps  
4.3 All ASTM test methods are required to include statements on precision and bias.3  
4.4 Since ASTM began to require all test methods to have precision and bias statements that are based on interlaboratory test methods, there has been increased concern regarding what statistical experiments and procedures to use during the development of the test methods. Although there exists a wide range of statistical procedures, there is a small group of generally accepted techniques that are beneficial to follow. This guide is designed to provide a brief overview of these procedures and to suggest an appropriate sequence of carrying out these procedures.  
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