1、Designation: D 6300 08An American National StandardStandard Practice forDetermination of Precision and Bias Data for Use in TestMethods for Petroleum Products and Lubricants1This standard is issued under the fixed designation D 6300; the number immediately following the designation indicates the yea
2、r 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.INTRODUCTIONBoth Research Report RR:D021007,2Manual on Determining
3、Precision Data for ASTM Methodson Petroleum Products and Lubricants2and the ISO 4259, benefitted greatly from more than 50 yearsof collaboration between ASTM and the Institute of Petroleum (IP) in the UK. The more recent workwas documented by the IP and has become ISO 4259.ISO 4259 encompasses both
4、the determination of precision and the application of such precisiondata. In effect, it combines the type of information in RR:D0210072regarding the determination ofthe precision estimates and the type of information in Practice D 3244 for the utilization of test data.The following practice, intende
5、d to replace RR:D021007,2differs slightly from related portions ofthe ISO standard.1. Scope1.1 This practice covers the necessary preparations andplanning for the conduct of interlaboratory programs for thedevelopment of estimates of precision (determinability, repeat-ability, and reproducibility) a
6、nd of bias (absolute and relative),and further presents the standard phraseology for incorporatingsuch information into standard test methods.1.2 This practice is generally limited to homogeneous prod-ucts with which serious sampling problems do not normallyarise.1.3 This practice may not be suitabl
7、e for solid or semisolidproducts such as petroleum coke, industrial pitches, paraffinwaxes, greases, or solid lubricants when the heterogeneousproperties of the substances create sampling problems. In suchinstances, use Practice E 691 or consult a trained statistician.2. Referenced Documents2.1 ASTM
8、 Standards:3D 123 Terminology Relating to TextilesD 3244 Practice for Utilization of Test Data to DetermineConformance with SpecificationsE29 Practice for Using Significant Digits in Test Data toDetermine Conformance with SpecificationsE 456 Terminology Relating to Quality and StatisticsE 691 Practi
9、ce for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 ISO Standards:ISO 4259 Petroleum Products-Determination and Applica-tion of Precision Data in Relation to Methods of Test43. Terminology3.1 Definitions:3.1.1 analysis of variance (ANOVA), na procedure fordividin
10、g the total variation of a set of data into two or moreparts, one of which estimates the error due to selecting andtesting specimens and the other part(s) possible sources ofadded variation. D 1233.1.2 bias, nthe difference between the population meanof the test results and an accepted reference val
11、ue. E 4563.1.3 bias, relative, nthe difference between the popula-tion mean of the test results and an accepted reference value,which is the agreed upon value obtained using an acceptedreference method for measuring the same property.3.1.4 degrees of freedom, nthe divisor used in the calcu-lation of
12、 variance.1This practice is under the jurisdiction of ASTM Committee D02 on PetroleumProducts and Lubricants and is the direct responsibility of Subcommittee D02.94 onCoordinating Subcommittee on Quality Assurance and Statistics.Current edition approved Dec. 15, 2008. Published February 2009. Origin
13、allyapproved in 1998. Last previous edition approved in 2007 as D 630007.2Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D021007.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Servi
14、ce at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4Available from International Organization for Standardization, 1 rue deVaremb, Case postale 56, CH-1211 Geneva 20, Switzerland.1Copyright ASTM International, 1
15、00 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.4.1 DiscussionThis definition applies strictly only inthe simplest cases. Complete definitions are beyond the scopeof this practice. ISO 42593.1.5 determinability, na quantitative measure of the vari-ability assoc
16、iated with the same operator in a given laboratoryobtaining successive determined values using the same appa-ratus for a series of operations leading to a single result; it isdefined as that difference between two such single determinedvalues as would be exceeded in the long run in only one casein 2
17、0 in the normal and correct operation of the test method.3.1.5.1 DiscussionThis definition implies that two deter-mined values, obtained under determinability conditions,which differ by more than the determinability value should beconsidered suspect. If an operator obtains more than twodetermination
18、s, then it would usually be satisfactory to checkthe most discordant determination against the mean of theremainder, using determinability as the critical difference (1).53.1.6 mean square, nin analysis of variance, a contractionof the expression “mean of the squared deviations from theappropriate a
19、verage(s)” where the divisor of each sum ofsquares is the appropriate degrees of freedom. D 1233.1.7 normal distribution, nthe distribution that has theprobability function:fx! 5 1/s!2p!21/2exp 2 x !2/2s2# (1)where:x = a random variate, = the mean distribution, ands = the standard deviation of the d
20、istribution.(Syn. Gaussian distribution, law of error) D 1233.1.8 outlier, na result far enough in magnitude fromother results to be considered not a part of the set.RR:D02100723.1.9 precision, nthe degree of agreement between two ormore results on the same property of identical test material. Inthi
21、s practice, precision statements are framed in terms ofrepeatability and reproducibility of the test method.3.1.9.1 DiscussionThe testing conditions represented byrepeatability and reproducibility should reflect the normalextremes of variability under which the test is commonly used.Repeatability co
22、nditions are those showing the least variation;reproducibility, the usual maximum degree of variability. Referto the definitions of each of these terms for greater detail.RR:D02100723.1.10 random error, nthe chance variation encounteredin all test work despite the closest control of variables.RR:D02
23、100723.1.11 repeatability, nthe quantitative expression of therandom error associated with the same operator in a givenlaboratory obtaining repetitive results by applying the same testmethod with the same apparatus under constant operatingconditions on identical test material within short intervals
24、oftime. It is defined as the difference between two such results atthe 95 % confidence level. RR:D02100723.1.11.1 DiscussionInterpret as the value equal to orbelow which the absolute difference between two single testresults obtained in the above conditions may expect to lie witha probability of 95
25、%. ISO 42593.1.11.2 DiscussionThe difference is related to the repeat-ability standard deviation but it is not the standard deviation orits estimate. RR:D02100723.1.12 reproducibility, na quantitative expression of therandom error associated with different operators from differentlaboratories using
26、different apparatus, each obtaining a singleresult by applying the same test method on an identical testsample. It is defined as the 95 % confidence limit for thedifference between two such single and independent results.3.1.12.1 DiscussionInterpret as the value equal to orbelow which the absolute d
27、ifference between two single testresults on identical material obtained by operators in differentlaboratories, using the standardized test, may be expected to liewith a probability of 95 %. ISO 42593.1.12.2 DiscussionThe difference is related to the repro-ducibility standard deviation but is not the
28、 standard deviationor its estimate. RR:D02100723.1.12.3 DiscussionIn those cases where the normal useof the test method does not involve sending a sample to atesting laboratory, either because it is an in-line test method orbecause of serious sample instabilities or similar reasons, theprecision tes
29、t for obtaining reproducibility may allow for theuse of apparatus from the participating laboratories at acommon site (several common sites, if feasible). The statisticalanalysis is not affected thereby. However, the interpretation ofthe reproducibility value will be affected, and therefore, theprec
30、ision statement shall, in this case, state the conditions towhich the reproducibility value applies.3.1.13 standard deviation, nthe most usual measure of thedispersion of observed values or results expressed as thepositive square root of the variance. E 4563.1.14 sum of squares, nin analysis of vari
31、ance, a con-traction of the expression “sum of the squared deviations fromthe appropriate average(s)” where the average(s) of interestmay be the average(s) of specific subset(s) of data or of theentire set of data. D 1233.1.15 variance, na measure of the dispersion of a seriesof accepted results abo
32、ut their average. It is equal to the sum ofthe squares of the deviation of each result from the average,divided by the number of degrees of freedom.RR:D02100723.1.16 variance, between-laboratory, nthat component ofthe overall variance due to the difference in the mean valuesobtained by different lab
33、oratories. ISO 42593.1.16.1 DiscussionWhen results obtained by more thanone laboratory are compared, the scatter is usually wider thanwhen the same number of tests are carried out by a singlelaboratory, and there is some variation between means obtainedby different laboratories. Differences in opera
34、tor technique,instrumentation, environment, and sample “as received” areamong the factors that can affect the between laboratoryvariance. There is a corresponding definition for between-operator variance.5The bold numbers in parentheses refers to the list of references at the end of thisstandard.D63
35、000823.1.16.2 DiscussionThe term “between-laboratory” is of-ten shortened to “laboratory” when used to qualify represen-tative parameters of the dispersion of the population of results,for example as “laboratory variance.”3.2 Definitions of Terms Specific to This Standard:3.2.1 determination, nthe p
36、rocess of carrying out a seriesof operations specified in the test method whereby a singlevalue is obtained.3.2.2 operator, na person who carries out a particular test.3.2.3 probability density function, nfunction which yieldsthe probability that the random variable takes on any one of itsadmissible
37、 values; here, we are interested only in the normalprobability.3.2.4 result, nthe final value obtained by following thecomplete set of instructions in the test method.3.2.4.1 DiscussionIt may be obtained from a single de-termination or from several determinations, depending on theinstructions in the
38、 method. When rounding off results, theprocedures described in Practice E29shall be used.4. Summary of Practice4.1 A draft of the test method is prepared and a pilotprogram can be conducted to verify details of the procedureand to estimate roughly the precision of the test method.4.2 A plan is devel
39、oped for the interlaboratory study usingthe number of participating laboratories to determine thenumber of samples needed to provide the necessary degrees offreedom. Samples are acquired and distributed. The interlabo-ratory study is then conducted on an agreed draft of the testmethod.4.3 The data a
40、re summarized and analyzed. Any depen-dence of precision on the level of test result is removed bytransformation. The resulting data are inspected for uniformityand for outliers. Any missing and rejected data are estimated.The transformation is confirmed. Finally, an analysis of vari-ance is perform
41、ed, followed by calculation of repeatability,reproducibility, and bias. When it forms a necessary part of thetest procedure, the determinability is also calculated.5. Significance and Use5.1 ASTM test methods are frequently intended for use inthe manufacture, selling, and buying of materials in acco
42、rdancewith specifications and therefore should provide such precisionthat when the test is properly performed by a competentoperator, the results will be found satisfactory for judging thecompliance of the material with the specification. Statementsaddressing precision and bias are required in ASTM
43、testmethods. These then give the user an idea of the precision ofthe resulting data and its relationship to an accepted referencematerial or source (if available). Statements addressing deter-minability are sometimes required as part of the test methodprocedure in order to provide early warning of a
44、 significantdegradation of testing quality while processing any series ofsamples.5.2 Repeatability and reproducibility are defined in theprecision section of every Committee D02 test method. Deter-minability is defined above in Section 3. The relationshipamong the three measures of precision can be
45、tabulated interms of their different sources of variation (see Table 1).5.2.1 When used, determinability is a mandatory part of theProcedure section. It will allow operators to check theirtechnique for the sequence of operations specified. It alsoensures that a result based on the set of determined
46、values isnot subject to excessive variability from that source.5.3 Abias statement furnishes guidelines on the relationshipbetween a set of test results and a related set of acceptedreference values. When the bias of a test method is known, acompensating adjustment can be incorporated in the testmet
47、hod.5.4 This practice is intended for use by D02 subcommitteesin determining precision estimates and bias statements to beused in D02 test methods. Its procedures correspond withISO 4259 and are the basis for the Committee D02 computersoftware, Calculation if Precision Data: Petroleum Test Meth-ods.
48、 The use of this practice replaces that of Research ReportRR:D021007.25.5 Standard practices for the calculation of precision havebeen written by many committees with emphasis on theirparticular product area. One developed by Committee E11 onStatistics is Practice E 691. Practice E 691 and this prac
49、ticediffer as outlined in Table 2.6. Stages in Planning of an Interlaboratory Test Programfor the Determination of the Precision of a TestMethod6.1 The stages in planning an interlaboratory test programare: preparing a draft method of test (see 6.2), planning andexecuting a pilot program with at least two laboratories(optional but recommended for new test methods) (see 6.3),planning the interlaboratory program (see 6.4), and executingthe interlaboratory program (see 6.5). The four stages aredescribed in turn.6.2 Preparing a Draft Me
