1、Designation: D4821 14Standard Guide forCarbon BlackValidation of Test Method Precision andBias1This standard is issued under the fixed designation D4821; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A
2、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 guide covers procedures for using the ASTMStandard Reference Blacks2(SRBs) and the HT and INRIodine Number Standards to continuous
3、ly monitor the preci-sion of those carbon black test methods for which referencevalues have been established. It also offers guidelines fortroubleshooting various test methods.1.2 This guide establishes procedures for the use of x-chartsto continuously monitor those tests listed in Section 2 forwith
4、in-lab precision (repeatability) and between-lab accuracy(reproducibility).1.3 This guide provides a statistical procedure for improv-ing test reproducibility when a laboratory cannot physicallycalibrate its apparatus to obtain the reference values of theASTM reference blacks, within the ranges give
5、n in this guide.2. Referenced Documents2.1 ASTM Standards:3D1510 Test Method for Carbon BlackIodine AdsorptionNumberD1513 Test Method for Carbon Black, PelletedPour Den-sityD1765 Classification System for Carbon Blacks Used inRubber ProductsD2414 Test Method for Carbon BlackOil AbsorptionNumber (OAN
6、)D3265 Test Method for Carbon BlackTint StrengthD3324 Practice for Carbon BlackImproving Test Repro-ducibility UsingASTM Standard Reference Blacks (With-drawn 2002)4D3493 Test Method for Carbon BlackOil AbsorptionNumber of Compressed Sample (COAN)D6556 Test Method for Carbon BlackTotal and ExternalS
7、urface Area by Nitrogen AdsorptionE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE2282 Guide for Defining the Test Result of a Test MethodE2586 Practice for Calculating and Using Basic Statistics3. Terminology3.1 Definitions:3.1.1 accepted reference value, na value that ser
8、ves as anagreed-upon reference for comparison, and which is derivedas: (1) a theoretical or established value, based on scientificprinciples, (2) an assigned or certified value, based on experi-mental work of some national or international organization, or(3) a consensus or certified value, based on
9、 collaborativeexperimental work under the auspices of a scientific orengineering group.3.1.1.1 DiscussionA national or internationalorganization, referred to in (2), generally maintains measure-ment standards to which the reference values obtained aretraceable. E1773.1.2 accuracy, nthe closeness of
10、agreement between atest result and an accepted reference value.3.1.2.1 DiscussionThe term accuracy, when applied to aset of test results, involves a combination of a randomcomponent and of a common systematic error or biascomponent. E1773.1.3 ASTM reference blacks, na set of carbon blacks thatspan t
11、he useful range of the test method for which they arereference materials. D33243.1.4 bias, nthe difference between the expectation of thetest results and an accepted reference value.1This guide is under the jurisdiction of ASTM Committee D24 on Carbon Blackand is the direct responsibility of Subcomm
12、ittee D24.61 on Carbon Black Samplingand Statistical Analysis.Current edition approved June 1, 2014. Published August 2014. Originallyapproved in 1988. Last previous edition approved in 2007 as D4821 071. DOI:10.1520/D4821-14.2Standard Reference Blacks are available from Laboratory Standards thus, “
13、standard deviation of test results amongoperators in a laboratory,” or “day-to-day standard deviationwithin a laboratory for the same operator.”3.1.7.2 DiscussionBecause the training of operators, theagreement of different pieces of equipment in the samelaboratory and the variation of environmental
14、conditions withlonger time intervals all depend on the degree of within-laboratory control, the intermediate measures of precision arelikely to vary appreciably from laboratory to laboratory. Thus,intermediate precisions may be more characteristic of indi-vidual laboratories than of the test method.
15、 E1773.1.8 intermediate precision conditions, nconditions un-der which test results are obtained with the same test methodusing test units or test specimens taken at random from a singlequantity of material that is as nearly homogeneous as possible,and with changing conditions such as operator, meas
16、uringequipment, location within the laboratory, and time. E1773.1.9 measured value, nan observed test results as op-posed to a standard value. D33243.1.10 normalization, nthe practice of applying a statisti-cal correction to test measurements to improve accuracy.3.1.10.1 DiscussionThe correction of
17、test data using astraight-line equation (linear regression) where measurementsof ASTM reference blacks are analyzed with published ac-cepted reference values to determine a slope and y-intercept.Normalization is a proven technique to improve the accuracyor reproducibility of laboratory data when all
18、 other means ofcalibration do not satisfactorily achieve a desired state ofcalibration.3.1.11 observation, nthe process of obtaining informationregarding the presence or absence of an attribute of a testspecimen, or of making a reading on a characteristic ordimension of a test specimen. E22823.1.12
19、observed value, nthe value obtained by making anobservation. E22823.1.13 precision, nthe closeness of agreement betweenindependent test results obtained under stipulated conditions.3.1.13.1 DiscussionPrecision depends on random errorsand does not relate to the accepted reference value.3.1.13.2 Discu
20、ssionThe measure of precision usually isexpressed in terms of imprecision and computed as a standarddeviation of the test results. Less precision is reflected by alarger standard deviation.3.1.13.3 Discussion“Independent test results” means re-sults obtained in a manner not influenced by any previou
21、sresult on the same or similar test object. Quantitative measuresof precision depend critically on the stipulated conditions.Repeatability and reproducibility conditions are particular setsof extreme stipulated conditions. E1773.1.14 regression of standard values on measured values,nstatistical equa
22、tion derived by the method of least-squares.D33243.1.15 repeatability, nprecision under repeatability condi-tions.3.1.15.1 DiscussionRepeatability is one of the concepts orcategories of the precision of a test method.3.1.15.2 DiscussionMeasures of repeatability defined inthis compilation are repeata
23、bility standard deviation and re-peatability limit. E1773.1.16 repeatability conditions, nconditions where inde-pendent test results are obtained with the same method onidentical test items in the same laboratory by the same operatorusing the same equipment within short intervals of time.3.1.16.1 Di
24、scussionSee precision, the “same operator,same equipment” requirement means that for a particular stepin the measurement process, the same combination of operatorand equipment is used for every test result. Thus, one operatormay prepare the test specimens, a second measure the dimen-sions and a thir
25、d measure the mass in a test method fordetermining density.3.1.16.2 DiscussionBy “in the shortest practical period oftime” is meant that the test results, at least for one material, areobtained in a time period not less than in normal testing and notso long as to permit significant change in test ma
26、terial,equipment or environment. E1773.1.17 repeatability limit (r), nthe value below which theabsolute difference between two individual test results obtainedunder repeatability conditions may be expected to occur with aprobability of approximately 0.95 (95 %).3.1.17.1 DiscussionThe repeatability l
27、imit is times therepeatability standard deviation. This multiplier is independentof the size of the interlaboratory study.3.1.17.2 DiscussionThe approximation to 0.95 is reason-ably good (say 0.90 to 0.98) when many laboratories (30 ormore) are involved, but is likely to be poor when fewer thaneight
28、 laboratories are studied. E1773.1.18 repeatability standard deviation (sr), nthe standarddeviation of test results obtained under repeatability condi-tions.3.1.18.1 DiscussionIt is a measure of the dispersion of thedistribution of test results under repeatability conditions.3.1.18.2 DiscussionSimil
29、arly, “repeatability variance”and “repeatability coefficient of variation” could be defined andused as measures of the dispersion of test results underrepeatability conditions.In an interlaboratory study, this isthe pooled standard deviation of test results obtained underrepeatability conditions.D48
30、21 1423.1.18.3 DiscussionThe repeatability standard deviation,usually considered a property of the test method, will generallybe smaller than the within-laboratory standard deviation. (Seewithin-laboratory standard deviation.) E1773.1.19 reproducibility, nprecision under reproducibilityconditions. E
31、1773.1.20 reproducibility conditions, nconditions where testresults are obtained with the same method on identical testitems in different laboratories with different operators usingdifferent equipment.3.1.20.1 DiscussionIdentical material means either thesame test units or test specimens are tested
32、by all thelaboratories as for a nondestructive test or test units or testspecimens are taken at random from a single quantity ofmaterial that is as nearly homogeneous as possible. A differentlaboratory of necessity means a different operator, differentequipment, and different location and under diff
33、erent supervi-sory control. E1773.1.21 reproducibility limit (R), nthe value below whichthe absolute difference between two test results obtained underreproducibility conditions may be expected to occur with aprobability of approximately 0.95 (95 %).3.1.21.1 DiscussionThe reproducibility limit is ti
34、mes thereproducibility standard deviation. The multiplier is indepen-dent of the size of the interlaboratory study (that is, of thenumber of laboratories participating).3.1.21.2 DiscussionThe approximation to 0.95 is reason-ably good (say 0.90 to 0.98) when many laboratories (30 ormore) are involved
35、 but is likely to be poor when fewer thaneight laboratories are studied. E1773.1.22 reproducibility standard deviation (sR), nthe stan-dard deviation of test results obtained under reproducibilityconditions.3.1.22.1 DiscussionOther measures of the dispersion oftest results obtained under reproducibi
36、lity conditions are the“reproducibility variance” and the “reproducibility coefficientof variation.”3.1.22.2 DiscussionThe reproducibility standard devia-tion includes, in addition to between laboratory variability, therepeatability standard deviation and a contribution from theinteraction of labora
37、tory factors (that is, differences betweenoperators, equipment and environments) with material factors(that is, the differences between properties of the materialsother than that property of interest). E1773.1.23 standard deviation, nof a population, , the squareroot of the average or expected value
38、 of the squared deviationof a variable from its mean; of a sample, s, the square root ofthe sum of the squared deviations of the observed values in thesample divided by the sample size minus one. E25863.1.24 standard value, nthe value assigned to a referenceblack by ASTM Committee D24 on Carbon Blac
39、k.3.1.24.1 DiscussionUsually this value is calculated as theaverage test result of an interlaboratory testing program.D33243.1.25 test determination, nthe value of a characteristic ordimension of a single test specimen derived from one or moreobserved values. E22823.1.26 test method, na definitive p
40、rocedure that producesa test result. E22823.1.27 test result, nthe value of a characteristic obtainedby carrying out a specified test method. E22823.1.28 test sample, nthe total quantity of material (con-taining one or more test specimens) needed to obtain a testresult as specified in the test metho
41、d. See test result. E22823.1.29 test specimen, nthe portion of a test sample neededto obtain a single test determination. E22823.1.30 trueness, nthe closeness of agreement between thepopulation mean of the measurements or test results and theaccepted reference value.3.1.30.1 Discussion“Population me
42、an” is, conceptually,the average value of an indefinitely large number of test results.E1773.1.31 variance, 2,s2,nsquare of the standard deviationof the population or sample. E25863.1.32 within-laboratory standard deviation, nthe stan-dard deviation of test results obtained within a laboratory for a
43、single material under conditions that may include such ele-ments as different operators, equipment, and longer timeintervals.3.1.32.1 DiscussionBecause the training of operators, theagreement of different pieces of equipment in the samelaboratory and the variation of environmental conditions withlon
44、ger time intervals depend on the degree of within-laboratorycontrol, the within-laboratory standard deviation is likely tovary appreciably from laboratory to laboratory. E1774. Significance and Use4.1 This guide recommends the use of statistical x-charts tographically monitor test data determined fo
45、r the ASTM refer-ence blacks for those test methods given in Section 2. Alllaboratories are encouraged to utilize statistical x-charts andASTM reference blacks because this enables a comparison oftesting precision within and between laboratories. The guidedescribes practices for the use of repeatabi
46、lity and reproduc-ibility limits and x-charts.4.2 In addition to the calibration of a test method byphysicochemical means, a statistical method for achievingcalibration of a test method is presented (that is, normaliza-tion).4.3 Poor test precision can be the result of poor repeatabilityor poor repr
47、oducibility or both. Causes may include inadequateoperator training, improperly maintained equipment or labora-tory environment, variation in sample preparation or analysistechniques, the lack of calibration or standardization ofinstrumentation, worn-out apparatus, reagents that do not meetspecifica
48、tions, different sources of instrumentation orequipment, and material heterogeneity. The sum of all sourcesof testing error is unique for an individual laboratory.4.4 Precision data for ASTM Reference Blacks are found inTables 1-3. These include standard reference blacks (SRBs)Series 8, HT and INR I
49、odine Standards. The HT or INR Iodinestandards are recommended for monitoring iodine testing.D4821 143TABLE 1 SRB-8 Precision by Test MethodTable 1A Precision Parameters for Test Method D1510, Iodine Number Method A see Test Method D2414),9.1.2.3 Error in oil delivery rate,9.1.2.4 Leaking oil delivery lines,9.1.2.5 Inadequate cleaning of CB-oil mixture from themixing assembly,9.1.2.6 Sample weight not accurate,9.1.2.7 Sample not dried,9.1.2.8 Sample not adequately cooled before weighing andtesting, and9.1.2.9 Mixing cha
