ASTM_E_1950_-_10.pdf

Designation:E195010Standard Practice forReporting Results from Methods of Chemical Analysis1This standard is issued under the fixed designation E1950;the number immediately following the designation indicates the year 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.1.Scope1.1 This practice covers the approximate number of digitsrequired to express the expected precision of results reportedfrom standard methods of chemical analysis.This practiceprovides selection criteria and proper form and symbols forcoding results when necessary to indicate the relative reliabilityof results having small values.1.2 Specifically excluded is consideration of report formsand the associated informational content of reports in whichresults are tabulated or transmitted.It is assumed that thereporting laboratory has established a report format to ensureproper identification of the materials tested,the nature andconditions of the test,the responsible personnel,and otherrelated information in accordance with existing regulations andgood laboratory practices.2.Referenced Documents2.1 ASTM Standards:2E29 Practice for Using Significant Digits in Test Data toDetermine Conformance with SpecificationsE135 Terminology Relating to Analytical Chemistry forMetals,Ores,and Related MaterialsE1601 Practice for Conducting an Interlaboratory Study toEvaluate the Performance of an Analytical MethodE1763 Guide for Interpretation and Use of Results fromInterlaboratory Testing of Chemical Analysis Methods3.Terminology3.1 Definitions:3.1.1 For definitions of terms,refer to Terminology E135.3.2 Definitions of Terms Specific to This Standard:3.2.1 lower limit,L,nthe lower limit of the quantitativeanalyte concentration range(see Annex A1).3.2.2 low-level reproducibility index,KR,nthe reproduc-ibility index constant(for low analyte levels)determined inaccordance with Guide E1763.3.2.3 null limit,NL,nthe analyte content below whichresults are so near zero that averaging is unlikely to yield avalue significantly different from zero.3.2.4 quantitative,adjrelating to results,having a numeri-cal value that includes at least one significant digit(see PracticeE29).4.Significance and Use4.1 Aresult must be stated to a sufficient number of digits sothat a user receives both quantitative information and ameasure of the variability of the value reported.4.2 The range of application of most methods of chemicalanalysis is based upon the presumption that the quantitativeresults produced are to be used to compare the analyte contentof the test material with specified limiting values.However,analytical results may be used legitimately for other purposes.If the same material is analyzed a number of times or a productis analyzed periodically during an interval of production,eachset of results may be averaged to yield an average result havingimproved reliability,provided nothing has been done betweenanalyses to modify the composition of the analyzed material.Results that fall below the lower limit,although not quantita-tive individually,contain compositional information and maybe reported.The reporting system in this practice permits theanalyst to indicate which values are likely to be renderedquantitative by averaging and which are not.4.3 The system is simple enough to be used routinely inreporting results from standard methods and assists thoseuntrained in statistics to apply results appropriately.5.Rounding Calculated Values5.1 Use information from the precision section of themethod to determine the appropriate number of digits to reportas follows:5.1.1 Estimate the reproducibility index,R,at the analytelevel of the result,C,from an equation of R as a function ofconcentration or from the table of statistical information.5.1.2 Calculate the percent relative reproducibility index:Rrel%5 1003R/C(1)1This practice is under the jurisdiction of ASTM Committee E01 on AnalyticalChemistry for Metals,Ores,and Related Materials and is the direct responsibility ofSubcommittee E01.22 on Laboratory Quality.Current edition approved Oct.1,2010.Published December 2010.Originallyapproved in 1998.Last previous edition approved in 2003 as E1950 98(2003).DOI:10.1520/E1950-10.2For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 5.1.3 For results within the range of application specified inthe method,round the values to the number of digits specifiedin Table 1(see A1.1.1 through A1.1.2).5.1.4 For results less than the lower limit,proceed inaccordance with Section 6 to establish the number of digits andappropriate coding for rounding