1、Designation: E2554 13E2554 18 An American National StandardStandard Practice forEstimating and Monitoring the Uncertainty of Test Resultsof a Test Method Using Control Chart Techniques1This standard is issued under the fixed designation E2554; the number immediately following the designation indicat
2、es the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice describes techniques for a labo
3、ratory to estimate the uncertainty of a test result using data from test results ona control sample. This standardpractice provides one method for a laboratory to estimate Measurement Uncertainty in accordancewith Section A22.3 in Form and Style offor ASTM Standards.1.2 Uncertainty as defined by thi
4、s practice applies to the capabilities of a single laboratory. Any estimate of uncertaintydetermined through the use of this practice applies only to the individual laboratory for which the data are presented.1.3 The laboratory uses a well defined and established test method in determining a series
5、of test results. The uncertaintyestimated using this practice only applies when the same test method is followed. The uncertainty only applies for the materialtypes represented by the control samples, and multiple control samples may be needed, especially if the method has differentprecision for dif
6、ferent sample types or response levels.1.4 The uncertainty estimate determined by this practice represents the intermediate precision of test results. This estimate seeksto quantify the total variation expected within a single laboratory using a single established test method while incorporating asm
7、any known sources of variation as possible.1.5 This practice does not establish error estimates (error budget) attributed to individual factors that could influenceuncertainty.1.6 This practice describes the use of control charts to evaluate the data obtained and presents a special type of control c
8、hartto monitor the estimate of uncertainty.1.7 The system of units for this standard is not specified. Dimensional quantities in the standard are presented only asillustrations of calculation methods. The examples are not binding on products or test methods treated.1.8 This standard does not purport
9、 to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine theapplicability of regulatory limitations prior to use.1.9 This international
10、 standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2.
11、 Referenced Documents2.1 ASTM Standards:2D5184 Test Methods for Determination of Aluminum and Silicon in Fuel Oils by Ashing, Fusion, Inductively Coupled PlasmaAtomic Emission Spectrometry, and Atomic Absorption SpectrometryE92 Test Methods for Vickers Hardness and Knoop Hardness of Metallic Materia
12、lsE177 Practice for Use of the Terms Precision and Bias in ASTM Test MethodsE384 Test Method for Microindentation Hardness of MaterialsE456 Terminology Relating to Quality and StatisticsE2282 Guide for Defining the Test Result of a Test Method1 This practice is under the jurisdiction of ASTM Committ
13、ee E11 on Quality and Statistics and is the direct responsibility of Subcommittee E11.20 on Test MethodEvaluation and Quality Control.Current edition approved April 1, 2013April 1, 2018. Published May 2013April 2018. Originally approved in 2007. Last previous edition approved in 20072013 as E2554 07
14、.13. DOI: 10.1520/E2554-13.10.1520/E2554-18.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is
15、not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropri
16、ate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1E2587 Practice for Use of Control Charts in Statistical Process C
17、ontrolISO/ASTM 51707 Guide for Estimating Uncertainties in Dosimetry for Radiation Processing2.2 ASTM Publications:2Form and Style for ASTM StandardsManual on Presentation of Data and Control ChartAnalysis7A Manual on Presentation of Data and Control ChartAnalysis: 7thEdition2.3 ISO Standard:3ISO/IE
18、C 17025 General Requirements for the Competence of Testing and Calibration Laboratories3. Terminology3.1 DefinitionsThe terminology of Terminology E456 applies to this practice except as modified herein.3.1.1 control sample, nsample taken from a stable, homogeneous material for the purposes of monit
19、oring the performance ofa test method in a laboratory.3.1.1.1 DiscussionThe control sample material is representative of the product typically tested in the laboratory by the given test method. A controlsample is run periodically using the complete test method protocol to develop a test result. Such
20、 test results may be statisticallyevaluated to monitor test method performance over time. It is not necessary to have an accepted reference value assigned to thecontrol sample material. When the current material is nearly consumed, a replacement material should be run in parallel with thecurrent mat
21、erial to ensure continuity in the control sample program.3.1.2 check sample, nsee control sample.3.1.3 intermediate precision, nthe closeness of agreement between test results obtained under specified intermediate precisionconditions. E1773.1.3.1 DiscussionThe specific measure and the specific condi
22、tions must be specified for each intermediate measure of precision; thus, “standarddeviation of test results among operators in a laboratory,” or “day-to-day standard deviation within a laboratory for the sameoperator.”3.1.3.2 DiscussionBecause the training of operators, the agreement of different p
23、ieces of equipment in the same laboratory and the variation ofenvironmental conditions with longer time intervals all depend on the degree of within- laboratory control, the intermediatemeasures of precision are likely to vary appreciably from laboratory to laboratory. Thus, intermediate precisions
24、may be morecharacteristic of individual laboratories than of the test method.3.1.4 test result, nthe value of a characteristic obtained by carrying out a specified test method. E22823.1.5 repeatability, nprecision under repeatability conditions. E1773.2 Definitions of Terms Specific to This Standard
25、:3.2.1 uncertainty control chart, ncontrol chart that includes control limits based on the variation attributed to the uncertaintyof the test method.4. Significance and Use4.1 This practice provides one way for a laboratory to develop data-based Type A estimates of uncertainty as referred to inSecti
26、on A22 in Form and Style offor ASTM Standards.4.2 Laboratories accredited under ISO/IEC 17025 are required to present uncertainty estimates for their test results. Thispractice provides procedures that use test results to develop uncertainty estimates for an individual laboratory.4.3 Generally, thes
27、e test results will be from a single sample of stable and homogeneous material known as a control or checksample.4.4 The true value of the characteristic(s) of the control sample being measured will ordinarily be unknown. However, thismethodology may also be used if the control sample is a reference
28、 material, in which case the test method bias may also be3 Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http:/www.ansi.org.E2554 182estimated and incorporated into the uncertainty estimate. Many test methods do not have true reference ma
29、terials available toprovide traceable chains of uncertainty estimation.4.5 This practice also allows for ongoing monitoring of the laboratory uncertainty. As estimates of the level of uncertaintychange, possibly as contributions to uncertainty are identified and minimized, revision to the laboratory
30、 uncertainty will bepossible.5. General Considerations5.1 Materials to be Used:5.1.1 This methodology requires a quantity of stable and homogeneous material which will serve as the source of controlsamples (sometimes called check samples). The material shall be similar in composition to the samples
31、of material routinelyanalyzed by this test method in this laboratory. By stable it is assumed that the test results obtained from this material should beconsistent over the time interval that this material will be used. By homogeneous it is assumed that samples taken from the materialsource will not
32、 have a significant variation in the characteristic measured by the test method.5.1.2 For destructive testing of control sample materials, provision shall be made for depletion and replacement of the controlsample material.5.1.2.1 In some cases, the test method may be nondestructive and the same mat
33、erial may be reused indefinitely.5.1.2.2 In other cases, the material may be used up, deteriorate, or otherwise gradually change.5.1.3 The test method should describe the best practices for preparing and storing the control material and taking the controlsamples.5.2 Test Conditions:5.2.1 An uncertai
34、nty estimation program should be designed to include all known sources of variation, such as operators(analysts), equipment, reagents, and so forth, and these should be deliberately incorporated into the design of the program. Ingeneral, these sources of variation will be defined (including acceptab
35、le tolerances) by the test method.5.2.2 In cases in which control over such variations is not possible or undefined, at least 30 to 50 sampling periods shall beevaluated to permit environmental and other factors to be incorporated in the overall estimate.6. Overall ProcedureControl Charting Methods6
36、.1 General concepts of control charts are described elsewhere. For more information, see Practice E2587 as well as Manual7A.6.2 The general procedure involves two major phases: Preliminary and Monitoring.6.2.1 Preliminary Phase:6.2.1.1 This phase begins with an initial collection of test results.6.2
37、.1.2 Preliminary control charts are then prepared and examined. These charts are evaluated to determine if the process is ina state of statistical control.The usual principles of control charting utilize short-term variability to estimate the limits within whichsamples of test results should vary. F
38、or control sample programs this short-term variability is equivalent to repeatability precision.It is expected, however, that additional contributions to variation will be present over time and therefore additional variation,equivalent to intermediate precision, will be encountered.6.2.1.3 An estima
39、te of uncertainty standard deviation is developed.6.2.1.4 An uncertainty control chart is then prepared to monitor future sample results.6.2.2 Monitoring Phase:6.2.2.1 The proposed uncertainty control chart is used to provide evidence that the estimate of uncertainty is not exceeding theestimated va
40、lue.6.2.2.2 The estimate of uncertainty should be periodically re-evaluated.6.2.2.3 Where appropriate, it is recommended that a standard control chart also be maintained to determine whether thevariation over time has been reduced to the level of short-term variation (repeatability).6.3 Two types of
41、 control charting methods are recommended to develop estimates of uncertainty. These include:6.3.1 Mean (Xbar) and range or standard deviation charts are used when multiple test results are conducted in each time period.6.3.2 Individual charts (IndX) are used when single test results are obtained in
42、 each time period.6.4 Variation Estimates:6.4.1 Either a range chart or a standard deviation chart may be used to estimate the short-term variability when multiple assaysare conducted under repeatability conditions per time period. An estimate from the control chart data can be compared to otheresti
43、mates of repeatability (within laboratory, short-term variation) if available.6.4.2 Sample averages are examined and may provide estimates of variation caused by other factors. Such factors may includeenvironmental effects, operator factors, reagents, or instruments.6.5 Systematic Procedures:6.5.1 S
44、pecifically designed experiments can be used to ensure all known sources of variation, such as operators (analysts),equipment, reagents, or instruments are incorporated in the general study.E2554 1836.5.2 The data generated from this program is available for additional uses, such as control charting
45、 to evaluate trends,stratification by analysis, or stratification by equipment to identify training or maintenance needs or both.7. Specific Procedures7.1 Multiple Test Results Generated Per Time Period:7.1.1 A specified number of independent test results are taken during each time period. Generally
46、 this number is 5 or less. Itis preferred that at least 25 sets of test results be obtained before developing the charts.7.1.2 Either a range chart or a standard deviation chart is prepared.This is examined for special cause variation. If the variabilityappears random then an estimate of repeatabili
47、ty is computed. This may be done by pooling the sums of squares, using the averagestandard deviation, or using the average range.NOTE 1If the ranges or standard deviations are zero in most of the samples, then this estimate of repeatability standard deviation is suspect andprobably unusable. This is
48、 usually the result of insufficient resolution of the measurement system in use or severe rounding. An estimate based on theminimum interval size should be substituted for the zeros. As a rule of thumb, consider replacing the zeros when more than about 13 are zeros.7.1.3 A means chart is used to exa
49、mine variation among time periods. Limits on this chart permit comparison of variationbetween time periods using repeatability as the estimate of error.7.1.3.1 If the control chart shows a state of statistical control then the uncertainty will be assumed approximately equivalent tothe repeatability standard deviation.7.1.3.2 In most cases it will be expected that the variability between means will show an “out of control” condition indicatingthat there are “special” causes of variation in addition to repeatability. The between means variation and within means repeat
