1、Designation:D 6518 03aStandard Practice forBias Testing a Mechanical Coal Sampling System1This standard is issued under the fixed designation D 6518;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number i
2、n parentheses indicates the year of last reapproval.Asuperscript epsilon(e)indicates an editorial change since the last revision or reapproval.1.Scope1.1 This practice presents sample collection and statisticalevaluation procedures for testing mechanical sampling sys-tems,subsystems,and individual s
3、ystem components for bias.It is the responsibility of the user of this practice to select theappropriate procedure for a specific sampling situation.1.2 This practice does not purport to define an absolute bias.Bias defined by this practice is the difference between thepopulation mean of the mechani
4、cal sampler test results and theaccepted reference value.1.3 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility
5、of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D 121 Terminology of Coal and CokeD 2013 Practice for Preparing Coal Samples for AnalysisD 2234 Practice for Collection of a Gross Sample of CoalD 4621 Guide for Quality Management in an Organizationthat Samples or Test
6、s Coal and CokeD 4702 Guide for Inspecting Crosscut,Sweep-Arm,andAuger Mechanical Coal Sampling Systems for Conform-ance with Current ASTM StandardsE 105 Practice for Probability Sampling of MaterialsE 122 Practice for Calculating Sample Size to Estimate,with a Specified Tolerable Error,the Average
7、for a Char-acteristic of a Lot or ProcessE 456 Terminology Relating to Quality and StatisticsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3.Terminology3.1 DefinitionsFor additional definitions of terms used inthis practice refer to Terminologies D
8、121 and E 456.3.2 Definitions of Terms Specific to This Standard:3.2.1 bias,nthe difference between the population meanof the mechanical sampler test results and the acceptedreference value.3.2.2 confidence interval,na numeric interval with alower limit and a higher limit within which the true param
9、etervalue is estimated to fall.The confidence interval percentageindicates the percentage of time the true value will fall withinthe interval if the procedure is continuously repeated.3.2.3 correlation,na measure of the linear dependencebetween paired system and reference measurements.Correla-tion f
10、requently is expressed by the correlation coefficient,which can take a value from minus one(perfect negative linearrelationship)to plus one(perfect positive linear relationship).3.2.4 delimitation error,na material error that occurswhen all the elements in a cross section of a coal stream do nothave
11、 an equal probability of being intercepted(captured)by thesampler cutter during increment collection.3.2.5 ellipsoidal region,nan area that is formed by planesections of ellipses that are defined by the values selected forthe largest tolerable bias of each coal characteristic used in thebias test.Th
12、e region will be used to determine if the system isbiased.3.2.6 Hotellings T2test,na statistical test that is used toevaluate multivariate data.It is the multivariate equivalent ofthe Students t-test.3.2.7 largest tolerable bias(LTB),nan interval whoseupper and lower bounds represent the limits of a
13、n acceptablebias.3.2.8 mechanical sampling system,na single machine orseries of interconnected machines whose purpose is to extractmechanically,or process(divide and reduce),or a combinationthereof,a sample of coal.3.2.9 paired data set,nsystem and reference values ob-served on samples collected and
14、 compared from the same batchof material.1This practice is under the jurisdiction of ASTM Committee D05 on Coal andCoke and is the direct responsibility of Subcommittee D05.23 on Sampling.Current edition approved Dec.1,2003.Published January 2004.Originallyapproved in 2000.Last previous edition appr
15、oved in 2003 as D 651803.2For referenced ASTM standards,visit 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.1Copyright ASTM International,100 Barr Ha
16、rbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.3.2.10 reference sample,na sample used in testing of amechanical sampling system which is comprised of one ormore increments collected from the test batch or lot of coal bythe stopped belt method as described in Practice D 2234.3.2.11 reject stream,nthe coal flow within a mechanicalsampling system,which occurs at each stage of division,beforeand after reduction,and is not included in the system sample.3.2.12 save stream,nthe co
