1、Designation: D 3244 07aAn American National StandardStandard Practice forUtilization of Test Data to Determine Conformance withSpecifications1This standard is issued under the fixed designation D 3244; the number immediately following the designation indicates the year oforiginal adoption or, in the
2、 case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.INTRODUCTIONThe properties of commercial petroleum products are measured by standardized laborator
3、y testmethods to check their conformance to specifications. Two or more measurements of the sameproperty of a specific sample by any given test method usually will not give precisely the same answer.Therefore, the test methods generally include a paragraph on the precision of results. This precision
4、is an expression of the reliability of the value of the measured property.Many difficulties that arise in interpreting specifications are due to test imprecision. Because of this,a true value of a property can never be determined exactly; and it is necessary to infer from measuredvalues the range wi
5、thin which the “true value” is likely to lie. The main purpose of this practice is toindicate how test imprecision should be interpreted relative to specification values.1. Scope1.1 This practice covers guidelines and statistical method-ologies with which two parties, usually a supplier and areceive
6、r, can compare and combine independently obtained testresults to obtain an Assigned Test Value (ATV) for the purposeof resolving a product quality dispute.1.2 This practice defines a technique for comparing anassigned test value with a specification limit.1.3 This practice applies only to those test
7、 methods whichspecifically state that the repeatability and reproducibilityvalues conform to the definitions herein.2. Referenced Documents2.1 ASTM Standards:2D 1319 Test Method for Hydrocarbon Types in LiquidPetroleum Products by Fluorescent Indicator AdsorptionD 4057 Practice for Manual Sampling o
8、f Petroleum andPetroleum ProductsD 4177 Practice for Automatic Sampling of Petroleum andPetroleum ProductsD 6300 Practice for Determination of Precision and BiasData for Use in Test Methods for Petroleum Products andLubricantsE29 Practice for Using Significant Digits in Test Data toDetermine Conform
9、ance with Specifications2.2 ISO Standard:3ISO 4259 Determination and Application of Precision Datain Relation to Methods of Test3. Terminology3.1 Definitions:3.1.1 acceptance limit (AL), na numerical value thatdefines the point between acceptable and unacceptable quality.3.1.1.1 DiscussionThe AL is
10、not necessarily the specifi-cation limit. It is a value that takes into account the specifica-tion value, the test method precision, and the confidence leveldesired for defining minimum acceptable quality relative to thespecification value.3.1.2 assigned test value (ATV), nthe average of all results
11、obtained in the several laboratories which are consideredacceptable based on the reproducibility of the test method.3.1.3 determination, nthe process of carrying out theseries of operations specified in the test method whereby asingle value is obtained.3.1.4 dispute, nwhen there is a question as to
12、productquality conformance to specification because a test valueobtained falls outside the specification limit(s).1This practice is under the jurisdiction of ASTM Committee D02 on PetroleumProducts and Lubricants and is the direct responsibility of D02.94 on CoordinatingSubcommittee on Quality Assur
13、ance and Statistics.Current edition approved Nov. 1, 2007. Published December 2007. Originallypublished as an appendix to the 1968 Annual Book of ASTM Standards, Part 18.Originally approved as a standard in 1974. Last previous edition approved in 2007as D 324407.2For referenced ASTM standards, visit
14、 the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York,
15、NY 10036, http:/www.ansi.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.5 operator, na person who normally and regularlycarries out a particular test.3.1.6 precision, nthe degree of agreement between two ormore results on th
16、e same property of identical test material. Inthis practice, precision statements are framed in terms of therepeatability and reproducibility of the test method.3.1.7 receiver, nany individual or organization who re-ceives or accepts the product delivered by the supplier.3.1.8 repeatability (r), nqu
17、antitative expression of therandom error associated with a single operator in a givenlaboratory obtaining replicate results with the same apparatusunder constant operating conditions on identical test materialwithin a short period of time. It is defined (3.1.8.1) as thatdifference between two such s
18、ingle results as would beexceeded in the long run in only 1 case in 20 in the normal andcorrect operation of the test method (3.1.8.3). (This is known asthe 95 % confidence level.)3.1.8.1 DiscussionThe repeatability and reproducibilityvalues should have been determined according to the methodsdescri
19、bed in ASTM Research Report RR:D02-1007, Manualon Determining Precision data for ASTM Methods of Petro-leum Products and Lubricants,4Practice D 6300,orISO 4259.3.1.8.2 DiscussionNot all standards organizations definerepeatability and reproducibility in precisely these same terms,and attention should
20、 always be paid to definitions beforecomparing precision values quoted.3.1.8.3 DiscussionThis difference is related to the repeat-ability or the reproducibility standard deviation but is not thestandard deviation.3.1.9 reproducibility (R), nquantitative expression of therandom error associated with
21、operators working in differentlaboratories, each obtaining single results on identical testmaterial when applying the same method. It is defined (3.1.8.1)as that difference between two such single and independentresults as would be exceeded in the long run in only 1 case in20 in the normal and corre
22、ct operation of the test method. See3.1.8.3.3.1.10 result, nthe value obtained by following the com-plete set of instructions of a test method. It may be obtainedfrom a single determination or several determinations, depend-ing on the instruction of the test method.3.1.11 supplier, nany individual o
23、r organization respon-sible for the quality of a product just before it is taken over bythe receiver.3.1.12 test sample, na portion of the product taken at theplace where the product is exchanged, that is, where theresponsibility for the product quality passes from the supplierto the receiver. In th
24、e event that this is not possible, a suitablesampling location should be mutually agreed upon.3.1.13 true value (), nfor practical purposes, the valuetowards which the average of single results obtained by Nlaboratories using the same standard test method tends, when Nbecomes very large. Consequentl
25、y, this definition of true valueis associated with the particular test method employed.4. Significance and Use4.1 This practice provides a means whereby the parties to atransaction can resolve potential quality disputes over thoseproduct properties which can be tested and expressed numeri-cally.4.1.
26、1 This practice can be used to ensure that such proper-ties are correctly stated on labels or in other descriptions of theproduct.4.1.2 This practice can be implemented in those cases wherea supplier uses an in-house or a commercial testing laboratoryto sample and test a product prior to releasing t
27、he product to ashipper (intermediate receiver) and the ultimate receiver alsouses an in-house or commercial testing laboratory to sampleand test the product upon arrival at the destination. Theassigned test value (ATV) would still be determined accordingto 8.3.4.2 This practice can assist in the det
28、ermination of toler-ances from specification limits which will ensure that the truevalue of a property is sufficiently close to the specificationvalue with a mutually agreed probability so that the product isacceptable to the receiver. Such tolerances are bounded by anacceptance limit (AL). If the A
29、TV value determined by applyingthis practice falls on the AL or on the acceptable side of the AL,the product can be accepted; otherwise it shall be deemed tohave failed the product acceptance requirement established byapplying this practice.4.3 Application of this practice requires the AL be deter-m
30、ined prior to actual commencement of testing. Therefore, thedegree of criticality of the specification, as determined by theProbability ofAcceptance (Pvalue) that is required to calculatethe AL, shall have been mutually agreed upon between bothparties prior to execution of actual product testing.4.3
31、.1 This agreement should include a decision as towhether the ATV is to be determined by the absolute orrounding-off method of Practice E29, as therein defined.4.3.1.1 If the rounding-off method is to be used, the numberof significant digits to be retained must also be agreed upon.4.3.1.2 These decis
32、ions must also be made in the case whereonly one party is involved, as in the case of a label.4.3.1.3 In the absence of such an agreement, this practicerecommends the ATV be rounded in accordance with therounding-off method in Practice E29to the number of signifi-cant digits that are specified in th
33、e governing specification.4.4 This practice is designed to be suitable for reference incontracts governing the transfer of petroleum products andlubricants from a supplier to a receiver.4.5 As a prerequisite for acceptance for lab test results to beused in this practice, the following conditions sha
34、ll be satisfied:4.5.1 Long-term standard deviation for the appropriate testmethod(s) from each lab, as substantiated by in-house qualitycontrol programs, on material typical of the product in dispute,shall be statistically equivalent or better than the publishedmethod standard deviation under reprod
35、ucibility conditions.4.5.2 Each lab shall be able to demonstrate, by way ofresults from interlaboratory exchange programs, a lack of asystemic bias relative to exchange averages for the appropriatetest method(s).4Supporting data have been filed at ASTM International Headquarters and maybe obtained b
36、y requesting Research Report RR:D02-1007.D 3244 07a24.5.3 In the event that the long-term standard deviation forany partys laboratory is not statistically equivalent to eachother, then, for the purpose of establishing the assigned testvalue (ATV), each laboratorys test result(s) shall be inverselywe
37、ighted in accordance with laboratorys demonstrated vari-ance(s).4.6 It is recommended that this practice be conducted underthe guidance of a qualified statistician.5. Sampling5.1 Sampling should be carried out as specified in accor-dance with the referenced test method, contract, or specifica-tion f
38、or the petroleum product under test, Practice D 4057,orPractice D 4177, as appropriate. Obtain enough sample toallow all required determinations to be made. Divide thesample into three secondary samples: a receiver sample, asupplier sample, and a retain sample. The retain sample shoulditself be larg
39、e enough to permit further subdivision into threeportions in case additional test work is desirable.6. Applying Test Method Precision Data to Accept orReject Test Results6.1 This section describes procedures in which the precisionlimits of test methods can be used as a decision criterion toaccept or
40、 reject test results obtained by two laboratories. Thissection can also be used for acceptance or rejection of resultsof replicate tests by an operator.6.2 Significance of Repeatability (r):6.2.1 Acceptance of ResultsWhen only two results areobtained under conditions of repeatability and the differe
41、nce isequal to or less than the repeatability of the method, theoperator may report the average of the two results as beingapplicable to the sample tested.6.2.2 Rejection of ResultsWhen two results are obtainedthat differ by more than the repeatability of the method, bothshould be rejected. Obtain t
42、wo additional results immediatelyunder conditions of repeatability. If the difference betweenthese two results is equal to or less than the repeatability of themethod, the operator should report the average of the two asbeing applicable to the sample tested. If, however, the differ-ence so obtained
43、again exceeds the repeatability, reject theresults and investigate the application of the method.6.3 Significance of Reproducibility (R):6.3.1 Acceptance of ResultsWhen two results are ob-tained and comprise one result from each laboratory (Note 1),if the difference is equal to or less than the repr
44、oducibility ofthe method, then both results should be considered acceptable.NOTE 1When a comparison for reproducibility is made betweenresults from two laboratories, it is a common practice that single resultsfrom each will be compared. If each of the laboratories has produced morethan a single resu
45、lt, see 6.4.6.3.2 Rejection of ResultsWhen the results from twolaboratories differ by more than the reproducibility of themethod, reject both results and each laboratory should repeatthe test on the retained sample. If the difference is now equalto or less than the reproducibility, both results shou
46、ld beconsidered acceptable. If, however, the difference betweenthese results is still greater than the reproducibility, reject theresults and investigate the application of the method at eachlaboratory.6.4 Significance of Reduced Reproducibility (R_reduced)from Multiple TestingIf the number of resul
47、ts obtained ineither one or both laboratories is more than one, then theallowable difference between the averages from the twolaboratories is given as follows:Difference, R_reduced 5R22 r2S112n112n2D(1)where:R = reproducibility of the method,r = repeatability of the method,n1= number of results of t
48、he first laboratory, andn2= number of results of the second laboratory.6.5 Referee LaboratoryIn the event a third or refereelaboratory is invited to perform the test using a portion of oneof the samples described in 6.3.2, multiply the reproducibility,R,by1.2 (to convert a range for two to a range f
49、or three) andcompare this value with the difference between the twoextreme results for acceptance. If acceptance is indicated, theassigned test value (ATV) for the sample should be the averageof the three results.7. Determination of Acceptance Limits by Applying TestMethod Precision Data and Specification CriticalityConsiderations to Specification Limits7.1 SpecificationsA specification fixes a limit to the truevalue of a given property. In practice, however, this true valuecan never be established exactly. The property is measured inthe laboratory by
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