1、Designation: D4821 14D4821 15Standard 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 revi
2、sion. 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 guide covers procedures for using theASTM Standard Reference Blacks2 (SRBs) and the HT and INR Iodine NumberStandards to c
3、ontinuously monitor the precision of those carbon black test methods for which reference values have beenestablished. It also offers guidelines for troubleshooting various test methods.1.2 This guide establishes procedures for the use of x-charts to continuously monitor those tests listed in Section
4、 2 for within-labprecision (repeatability) and between-lab accuracy (reproducibility).1.3 This guide provides a statistical procedure for improving test reproducibility when a laboratory cannot physically calibrateits apparatus to obtain the reference values of the ASTM reference blacks, within the
5、ranges given in this guide.2. Referenced Documents2.1 ASTM Standards:3D1510 Test Method for Carbon BlackIodine Adsorption NumberD1513 Test Method for Carbon Black, PelletedPour DensityD1765 Classification System for Carbon Blacks Used in Rubber ProductsD2414 Test Method for Carbon BlackOil Absorptio
6、n Number (OAN)D3265 Test Method for Carbon BlackTint StrengthD3324 Practice for Carbon BlackImproving Test Reproducibility Using ASTM Standard Reference Blacks (Withdrawn2002)4D3493 Test Method for Carbon BlackOil Absorption Number of Compressed Sample (COAN)D6556 Test Method for Carbon BlackTotal a
7、nd External Surface Area by Nitrogen AdsorptionE177 Practice for Use of the Terms Precision and Bias in ASTM 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
8、value that serves as an agreed-upon reference for comparison, and which is derived as: (1)a theoretical or established value, based on scientific principles, (2) an assigned or certified value, based on experimental work ofsome national or international organization, or (3) a consensus or certified
9、value, based on collaborative experimental work underthe auspices of a scientific or engineering group.3.1.1.1 Discussion1 This guide is under the jurisdiction of ASTM Committee D24 on Carbon Black and is the direct responsibility of Subcommittee D24.61 on Carbon Black Sampling andStatistical Analys
10、is.Current edition approved June 1, 2014Jan. 1, 2015. Published August 2014February 2015. Originally approved in 1988. Last previous edition approved in 20072014 asD4821 07D4821 14.1. DOI: 10.1520/D4821-14.10.1520/D4821-15.2 Standard Reference Blacks are available from Laboratory Standards thus, “st
11、andarddeviation of test results among operators in a laboratory,” or “day-to-day standard deviation within a laboratory for the sameoperator.”3.1.7.2 DiscussionBecause the training of operators, the agreement of different pieces of equipment in the same laboratory and the variation ofenvironmental c
12、onditions 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 may be morecharacteristic of individual laboratories than of the test method.
13、E1773.1.8 intermediate precision conditions, nconditions under which test results are obtained with the same test method using testunits or test specimens taken at random from a single quantity of material that is as nearly homogeneous as possible, and withchanging conditions such as operator, measu
14、ring equipment, location within the laboratory, and time. E1773.1.9 measured value, nan observed test results as opposed to a standard value. D33243.1.10 normalization, nthe practice of applying a statistical correction to test measurements to improve accuracy.3.1.10.1 DiscussionThe correction of te
15、st data using a straight-line equation (linear regression) where measurements of ASTM reference blacks areanalyzed with published accepted reference values to determine a slope and y-intercept. Normalization is a proven technique toimprove the accuracy or reproducibility of laboratory data when all
16、other means of calibration do not satisfactorily achieve adesired state of calibration.3.1.11 observation, nthe process of obtaining information regarding the presence or absence of an attribute of a test specimen,or of making a reading on a characteristic or dimension of a test specimen. E22823.1.1
17、2 observed value, nthe value obtained by making an observation. E22823.1.13 precision, nthe closeness of agreement between independent test results obtained under stipulated conditions.3.1.13.1 DiscussionD4821 152Precision depends on random errors and does not relate to the accepted reference value.
18、3.1.13.2 DiscussionThe measure of precision usually is expressed in terms of imprecision and computed as a standard deviation of the test results. Lessprecision is reflected by a larger standard deviation.3.1.13.3 Discussion“Independent test results” means results obtained in a manner not influenced
19、 by any previous result on the same or similar testobject. Quantitative measures of precision depend critically on the stipulated conditions. Repeatability and reproducibilityconditions are particular sets of extreme stipulated conditions. E1773.1.14 regression of standard values on measured values,
20、 nstatistical equation derived by the method of least-squares. D33243.1.15 repeatability, nprecision under repeatability conditions.3.1.15.1 DiscussionRepeatability is one of the concepts or categories of the precision of a test method.3.1.15.2 DiscussionMeasures of repeatability defined in this com
21、pilation are repeatability standard deviation and repeatability limit. E1773.1.16 repeatability conditions, nconditions where independent test results are obtained with the same method on identical testitems in the same laboratory by the same operator using the same equipment within short intervals
22、of time.3.1.16.1 DiscussionSee precision, the “same operator, same equipment” requirement means that for a particular step in the measurement process, thesame combination of operator and equipment is used for every test result. Thus, one operator may prepare the test specimens, asecond measure the d
23、imensions and a third measure the mass in a test method for determining density.3.1.16.2 DiscussionBy “in the shortest practical period of time” is meant that the test results, at least for one material, are obtained in a time periodnot less than in normal testing and not so long as to permit signif
24、icant change in test material, equipment or environment. E1773.1.17 repeatability limit (r), nthe value below which the absolute difference between two individual test results obtainedunder repeatability conditions may be expected to occur with a probability of approximately 0.95 (95 %).3.1.17.1 Dis
25、cussionThe repeatability limit is times the repeatability standard deviation. This multiplier is independent of the size of the interlaboratorystudy.3.1.17.2 DiscussionThe approximation to 0.95 is reasonably good (say 0.90 to 0.98) when many laboratories (30 or more) are involved, but is likelyto be
26、 poor when fewer than eight laboratories are studied. E1773.1.18 repeatability standard deviation (sr), nthe standard deviation of test results obtained under repeatability conditions.3.1.18.1 DiscussionIt is a measure of the dispersion of the distribution of test results under repeatability conditi
27、ons.3.1.18.2 DiscussionD4821 153Similarly, “repeatability variance” and “repeatability coefficient of variation” could be defined and used as measures of thedispersion of test results under repeatability conditions.In an interlaboratory study, this is the pooled standard deviation of testresults obt
28、ained under repeatability conditions.3.1.18.3 DiscussionThe repeatability standard deviation, usually considered a property of the test method, will generally be smaller than thewithin-laboratory standard deviation. (See within-laboratory standard deviation.) E1773.1.19 reproducibility, nprecision u
29、nder reproducibility conditions. E1773.1.20 reproducibility conditions, nconditions where test results are obtained with the same method on identical test items indifferent laboratories with different operators using different equipment.3.1.20.1 DiscussionIdentical material means either the same tes
30、t units or test specimens are tested by all the laboratories as for a nondestructive testor test units or test specimens are taken at random from a single quantity of material that is as nearly homogeneous as possible.A different laboratory of necessity means a different operator, different equipmen
31、t, and different location and under differentsupervisory control. E1773.1.21 reproducibility limit (R), nthe value below which the absolute difference between two test results obtained underreproducibility conditions may be expected to occur with a probability of approximately 0.95 (95 %).3.1.21.1 D
32、iscussionThe reproducibility limit is times the reproducibility standard deviation. The multiplier is independent of the size of theinterlaboratory study (that is, of the number of laboratories participating).3.1.21.2 DiscussionThe approximation to 0.95 is reasonably good (say 0.90 to 0.98) when man
33、y laboratories (30 or more) are involved but is likelyto be poor when fewer than eight laboratories are studied. E1773.1.22 reproducibility standard deviation (sR), nthe standard deviation of test results obtained under reproducibilityconditions.3.1.22.1 DiscussionOther measures of the dispersion of
34、 test results obtained under reproducibility conditions are the “reproducibility variance” andthe “reproducibility coefficient of variation.”3.1.22.2 DiscussionThe reproducibility standard deviation includes, in addition to between laboratory variability, the repeatability standard deviationand a co
35、ntribution from the interaction of laboratory factors (that is, differences between operators, equipment and environments)with material factors (that is, the differences between properties of the materials other than that property of interest). E1773.1.23 standard deviation, nof a population, , the
36、square root of the average or expected value of the squared deviation ofa variable from its mean; of a sample, s, the square root of the sum of the squared deviations of the observed values in the sampledivided by the sample size minus one. E25863.1.24 standard value, nthe value assigned to a refere
37、nce black by ASTM Committee D24 on Carbon Black.3.1.24.1 DiscussionUsually this value is calculated as the average test result of an interlaboratory testing program. D33243.1.25 test determination, nthe value of a characteristic or dimension of a single test specimen derived from one or moreobserved
38、 values. E22823.1.26 test method, na definitive procedure that produces a test result. E2282D4821 1543.1.27 test result, nthe value of a characteristic obtained by carrying out a specified test method. E22823.1.28 test sample, nthe total quantity of material (containing one or more test specimens) n
39、eeded to obtain a test result asspecified in the test method. See test result. E22823.1.29 test specimen, nthe portion of a test sample needed to obtain a single test determination. E22823.1.30 trueness, nthe closeness of agreement between the population mean of the measurements or test results and
40、theaccepted reference value.3.1.30.1 Discussion“Population mean” is, conceptually, the average value of an indefinitely large number of test results. E1773.1.31 variance, 2, s2, nsquare of the standard deviation of the population or sample. E25863.1.32 within-laboratory standard deviation, nthe stan
41、dard deviation of test results obtained within a laboratory for a singlematerial under conditions that may include such elements as different operators, equipment, and longer time intervals.3.1.32.1 DiscussionBecause the training of operators, the agreement of different pieces of equipment in the sa
42、me laboratory and the variation ofenvironmental conditions with longer time intervals depend on the degree of within-laboratory control, the within-laboratorystandard deviation is likely to vary appreciably from laboratory to laboratory. E1774. Significance and Use4.1 This guide recommends the use o
43、f statistical x-charts to graphically monitor test data determined for the ASTM referenceblacks for those test methods given in Section 2.All laboratories are encouraged to utilize statistical x-charts andASTM referenceblacks because this enables a comparison of testing precision within and between
44、laboratories. The guide describes practices forthe use of repeatability and reproducibility limits and x-charts.4.2 In addition to the calibration of a test method by physicochemical means, a statistical method for achieving calibration ofa test method is presented (that is, normalization).4.3 Poor
45、test precision can be the result of poor repeatability or poor reproducibility or both. Causes may include inadequateoperator training, improperly maintained equipment or laboratory environment, variation in sample preparation or analysistechniques, the lack of calibration or standardization of inst
46、rumentation, worn-out apparatus, reagents that do not meetspecifications, different sources of instrumentation or equipment, and material heterogeneity.The sum of all sources of testing erroris unique for an individual laboratory.4.4 Precision data forASTM Reference Blacks are found in Tables 1-3. T
47、hese include standard reference blacks (SRBs) Series8, HT and INR Iodine Standards. The HT or INR Iodine standards are recommended for monitoring iodine testing.NOTE 1Preferred precision values are bolded in Tables 1-3.5. Guide to Accepted Normalization Practices for Carbon Black Test Methods5.1 Acc
48、epted normalization practices for test methods found in Classification D1765, Table 1 are described below.5.1.1 Test Method D1510, Iodine NumberTest Method D1510 contains instructions on how to perform a normalization of thetest results. The HT or INR Iodine reference materials are recommended for m
49、onitoring iodine testing. The SRB HT and INRreference materials are specially prepared carbon blacks that have been shown to have stable iodine number values over a periodof many years. If normalization is required, it shall be done using only the SRB HT or INR reference material values as given inTable 2 and Table 3. Typically, this test method does not require normalization unless the HT or INR reference material values arenot within the published precision or accuracy limits, or both. The statistical correction d
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