1、Designation: D4821 15D4821 16Standard 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 defines the environmental conditions that are required for laboratories that perform carbon black te
4、sting activitiesfor those test methods under D24s jurisdiction.1.3 This guide establishes procedures for the use of x-charts to continuously monitor those tests listed in Section 2 for within-labprecision (repeatability) and between-lab accuracy (reproducibility).1.4 This guide provides a statistica
5、l procedure for improving test reproducibility when a laboratory cannot physically calibrateits apparatus to obtain the reference values of the ASTM reference blacks, within the ranges given in this guide.2. Referenced Documents2.1 ASTM Standards:3D1510 Test Method for Carbon BlackIodine Adsorption
6、NumberD1513 Test Method for Carbon Black, PelletedPour DensityD1765 Classification System for Carbon Blacks Used in Rubber ProductsD2414 Test Method for Carbon BlackOil Absorption Number (OAN)D3265 Test Method for Carbon BlackTint StrengthD3324 Practice for Carbon BlackImproving Test Reproducibility
7、 Using ASTM Standard Reference Blacks (Withdrawn2002)4D3493 Test Method for Carbon BlackOil Absorption Number of Compressed Sample (COAN)D6556 Test Method for Carbon BlackTotal and External Surface Area by Nitrogen AdsorptionE177 Practice for Use of the Terms Precision and Bias in ASTM Test MethodsE
8、2282 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 serves as an agreed-upon reference for comparison, and which is derived as: (1)a theoretical or established val
9、ue, 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 value, based on collaborative experimental work underthe auspices of a scientific or engineering group.3.1.1.1 Discussion1
10、 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 Analysis.Current edition approved Jan. 1, 2015July 1, 2016. Published February 2015August 2016. Originally approved in 1988. Las
11、t previous edition approved in 20142015 asD4821 14.D4821 15. DOI: 10.1520/D4821-15.10.1520/D4821-16.2 Standard Reference Blacks are available from Laboratory Standards thus, “standarddeviation of test results among operators in a laboratory,” or “day-to-day standard deviation within a laboratory for
12、 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 conditions with longer time intervals all depend on the degree of within-laboratory control, the intermediatemeasures of pre
13、cision are likely to vary appreciably from laboratory to laboratory. Thus, intermediate precisions may be morecharacteristic of individual laboratories than of the test method. E1773.1.8 intermediate precision conditions, nconditions under which test results are obtained with the same test method us
14、ing 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, measuring equipment, location within the laboratory, and time. E1773.1.9 measured value, nan observed test results as opposed to
15、 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 test data using a straight-line equation (linear regression) where measurements of ASTM reference blacks areanalyzed with pub
16、lished 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 other means of calibration do not satisfactorily achieve adesired state of calibration.3.1.11 observation, nthe process of
17、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. E22823.1.12 observed value, nthe value obtained by making an observation. E22823.1.13 precision, nthe closeness of agreement between
18、independent test results obtained under stipulated conditions.3.1.13.1 DiscussionD4821 162Precision depends on random errors and does not relate to the accepted reference value.3.1.13.2 DiscussionThe measure of precision usually is expressed in terms of imprecision and computed as a standard deviati
19、on 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 by any previous result on the same or similar testobject. Quantitative measures of precision depend critically on the stip
20、ulated conditions. Repeatability and reproducibilityconditions are particular sets of extreme stipulated conditions. E1773.1.14 regression of standard values on measured values, nstatistical equation derived by the method of least-squares. D33243.1.15 repeatability, nprecision under repeatability co
21、nditions.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 compilation are repeatability standard deviation and repeatability limit. E1773.1.16 repeatability conditions, nconditions whe
22、re 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 of time.3.1.16.1 DiscussionSee precision, the “same operator, same equipment” requirement means that for a particular step
23、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 dimensions and a third measure the mass in a test method for determining density.3.1.16.2 DiscussionBy “in the shortest prac
24、tical 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 significant change in test material, equipment or environment. E1773.1.17 repeatability limit (r), nthe value below which the abs
25、olute 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 DiscussionThe repeatability limit is times the repeatability standard deviation. This multiplier is independent of the size of
26、 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 poor when fewer than eight laboratories are studied. E1773.1.18 repeatability standard deviation (sr), nthe standard devia
27、tion 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 conditions.3.1.18.2 DiscussionD4821 163Similarly, “repeatability variance” and “repeatability coefficient of variation” could be d
28、efined and used as measures of thedispersion of test results under repeatability conditions.In an interlaboratory study, this is the pooled standard deviation of testresults obtained under repeatability conditions.3.1.18.3 DiscussionThe repeatability standard deviation, usually considered a property
29、 of the test method, will generally be smaller than thewithin-laboratory standard deviation. (See within-laboratory standard deviation.) E1773.1.19 reproducibility, nprecision under reproducibility conditions. E1773.1.20 reproducibility conditions, nconditions where test results are obtained with th
30、e same method on identical test items indifferent laboratories with different operators using different equipment.3.1.20.1 DiscussionIdentical material means either the same test units or test specimens are tested by all the laboratories as for a nondestructive testor test units or test specimens ar
31、e 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 equipment, and different location and under differentsupervisory control. E1773.1.21 reproducibility limit (R), nthe value below wh
32、ich 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 DiscussionThe reproducibility limit is times the reproducibility standard deviation. The multiplier is independent of the si
33、ze 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 many laboratories (30 or more) are involved but is likelyto be poor when fewer than eight laboratories are studied. E1773.1.22
34、 reproducibility standard deviation (sR), nthe standard deviation of test results obtained under reproducibilityconditions.3.1.22.1 DiscussionOther measures of the dispersion of test results obtained under reproducibility conditions are the “reproducibility variance” andthe “reproducibility coeffici
35、ent of variation.”3.1.22.2 DiscussionThe reproducibility standard deviation includes, in addition to between laboratory variability, the repeatability standard deviationand a contribution from the interaction of laboratory factors (that is, differences between operators, equipment and environments)w
36、ith 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 square root of the average or expected value of the squared deviation ofa variable from its mean; of a sample, s, the squar
37、e 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 reference black by ASTM Committee D24 on Carbon Black.3.1.24.1 DiscussionUsually this value is calculated as the average test res
38、ult 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 values. E22823.1.26 test method, na definitive procedure that produces a test result. E2282D4821 1643.1.27 test result, nt
39、he 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) needed to obtain a test result asspecified in the test method. See test result. E22823.1.29 test specimen, nthe portion of a
40、 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 theaccepted reference value.3.1.30.1 Discussion“Population mean” is, conceptually, the average value of an indefinitely lar
41、ge 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 standard deviation of test results obtained within a laboratory for a singlematerial under conditions that may include such ele
42、ments 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 same laboratory and the variation ofenvironmental conditions with longer time intervals depend on the degree of within-labora
43、tory control, the within-laboratorystandard deviation is likely to vary appreciably from laboratory to laboratory. E1774. Significance and Use4.1 This guide provides insight into the environmental conditions required for operation of laboratories or to aid in the designof new laboratories that perfo
44、rm carbon black testing activities using those test methods that are under D24s jurisdiction. Thisguide does not supersede any specific requirements a laboratory may choose to establish.4.2 This guide recommends the use of statistical x-charts to graphically monitor test data determined for the ASTM
45、 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 laboratories. The guide describes practices forthe use of repeatability and rep
46、roducibility limits and x-charts.4.3 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).4.4 Poor test precision can be the result of poor repeatability or poor reproducibility
47、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 instrumentation, worn-out apparatus, reagents that do not meetspecifications, diffe
48、rent sources of instrumentation or equipment, and material heterogeneity.The sum of all sources of testing erroris unique for an individual laboratory.4.5 Precision data forASTM Reference Blacks are found in Tables 1-3. These include standard reference blacks (SRBs) Series8, HT and INR Iodine Standa
49、rds. The HT or INR Iodine standards are recommended for monitoring iodine testing.NOTE 1Preferred precision values are bolded in Tables 1-3.5. Laboratory Environmental Conditions5.1 Test methods under the jurisdiction of D24 have no specific requirements for controlling laboratory temperature or relativehumidity. The environmental condition in a laboratory is just one of many factors that can impact precision. The followingrecommendations are offered to help reduce the impact of environmental conditions on a laborat
