# ASTM D6607-00 (Reapproved 2015)

Designation: D6607 − 00 (Reapproved 2015)Standard Practice forInclusion of Precision Statement Variation in SpecificationLimits1This standard is issued under the fixed designation D6607; 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 a method of determining rationalspecification limits by inclusion of the precision of the testmethod used in the specification.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.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 of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C670 Practice for Preparing Precision and Bias Statementsfor Test Methods for Construction MaterialsC802 Practice for Conducting an Interlaboratory Test Pro-gram to Determine the Precision of Test Methods forConstruction MaterialsD2172 Test Methods for Quantitative Extraction of BitumenFrom Bituminous Paving MixturesD2726 Test Method for Bulk Specific Gravity and Densityof Non-Absorptive Compacted Bituminous MixturesE177 Practice for Use of the Terms Precision and Bias inASTM Test Methods2.2 Federal Highway Administration Report:FHWA Report HI-93–047 Materials Control andAcceptance—Quality Assurance, Federal HighwayAdministration, May 199333. Terminology3.1 For definitions of terms used in this practice, consultPractice E177.4. Significance and Use4.1 Each test method has a limited precision. Even if a testis performed as carefully and as correctly as possible on amaterial which is as homogeneous as can be obtained, the testwill still vary from one to another. A widely used measure ofthe variation of the test results from a test method is thestandard deviation (σ). In an ASTM standard test, the standarddeviation of the test method can be found in the Precision andBias statement for the test. The “Blue Book,” Form and Stylefor ASTM Standards, requires that all test methods includePrecision and Bias statements. Practice C670 and PracticeC802 provide guidance for determination of these values.4.2 If the precision of a test method is low and the precisionof the test has not been properly considered in a materialspecification, a uniform material with the right quality may stillbe rejected most of the time because of the wide variation ofthe test results. In order to have rational specification limits, theprecision of the test used should be properly included in aspecification.4.3 This practice provides a guideline for proper inclusionof precision of the test method in a rational specification.5. Procedure5.1 Determine the effective standard deviation (σX)ofthetest results due to the combined effects of materials variationand test variation using Eq 1:σX5 ~σM21σT2! (1)where:σM= standard deviation of test property due to materialvariation (see Note 1), andσT= standard deviation of test property due to test method(see Note 2).NOTE 1—σMis the expected standard deviation of the material propertywhen the material is produced in a properly controlled process.Astandarddeviation which is representative of the acceptable variation of thematerial can be used. It can be calculated from the data obtained fromproperly produced materials.1This practice is under the jurisdiction of Committee D04 on Road and PavingMaterials and is the direct responsibility of Subcommittee D04.94 on StatisticalProcedures and Evaluation of Data.Current edition approved Jan. 1, 2015. Published February 2015. Originallyapproved in 2000. Last previous edition approved in 2009 as D6607 – 00 (2009).DOI: 10.1520/D6607-00R15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at service@astm.org. For Annual Book of ASTMStandards volume information, refer to the standard’s Document Summary page onthe ASTM website.3Available from National Technical Information Service (NTIS), U.S. Depart-ment of Commerce, 5285 Port Royal Rd., Springfield, VA 22161.Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1NOTE 2—σTis the standard deviation as given in the precision statementfor the test method used to measure the test property.5.2 Determine the standard deviation of the mean of the testresults~σ3¯!using Eq 2:σ3¯ 5 σ3/=n (2)where:n = number of tests performed.5.3 For a two-ended specification (with both a minimumand maximum limits), the specification limits for the averagetest value from n test ~x¯! should be the following:µ 2 Zα/2σ3¯# 3¯#µ1Zα/2σ3¯ (3)where:µ = target propertyZα/2= critical number of standard deviations for (1–α) con-fidence interval. (See Table 1 for values of Zα /2fordifferent specified confidence intervals.)5.4 For a one-ended specification (with only a maximum orminimum limit), the specification limit for the average testvalue from n test ~x¯! should be the following:3¯$µ 2 Zασ3¯~with a minimum limit! (4)or3¯#µ1Zασ3¯~with a maximum limit! (5)APPENDIXESX1. First Example of the Application of Precision Limits to Specification WritingX1.1 Problem StatementX1.1.1 A specification is to be written for the asphaltcontent of an asphalt mixture with aggregate water absorptioncapacity of less than 1.25 %. Three reflux asphalt extractiontests are to be run and the average of three test results is to beused for acceptance purpose. The target asphalt content is6.2 %. It is assumed that the contractor can reasonably controlthe asphalt content with a standard deviation of 0.20 % (seeNote X1.1).NOTE X1.1—Typical standard deviations of different material propertiescan be found in FHWA Report HI-93–047. The typical range of standarddeviation of asphalt content was given as 0.15 % – 0.30 %.X1.2 Precision statement for Test Methods D2172 (MethodB—Reflux) is given in Table X1.1.X1.3 The combined standard deviation of the measuredasphalt content:σx5=~0.2210.232! 5 0.305% (X1.1)X1.4 The standard deviation of the mean of three testresults:σx¯5 0.305/= 3 5 0.176% (X1.2)X1.5 Specification limits using a 95 % confidence interval:56.2%6Zα/2~0.176%! (X1.3)56.2%61.96 ~0.176%!56.2 %60.3%TABLE1ZValuesforDifferentConfidence LevelsConfidenceLevel (1 – α):90 % 95 % 97.5 % 99.0 %Zα/2(Two-EndSpecification)1.645 1.960 2.243 2.575Zα(One-EndSpecification)1.282 1.645 1.960 2.327TABLE X1.1 Mixes with Agg. of Water Absorption 1.25 %StandardDeviationAcceptable Range ofTwo Test ResultsSingle-Operator 0.19 % .054 %Multi-Operator 0.23 % 0.65 %D6607 − 00 (2015)2X2. Second ExampleX2.1 Problem StatementX2.1.1 A specification is to be written for the asphaltcontent of the asphalt mixture as described in Example 1.However, the average of seven test results (instead of three testresults) is to be used.X2.2 The combined standard deviation of the measuredasphalt content is the same as in Example 1:σx5=~0.2210.232! 5 0.305% (X2.1)X2.3 The standard deviation of the mean of seven testresults:σx¯5 0.305/= 7 5 0.115% (X2.2)X2.4 Specification limits using a 95 % confidence interval:56.2%61.96 ~0.115%! (X2.3)56.2%60.2%X3. Third ExampleX3.1 Problem StatementX3.1.1 A specification is to be written for the compacteddensity of an asphalt mixture with non-absorptive aggregate.The target density is 2.365 g/cm3. Five density measurementsin accordance with Test Method D2726 are to be made, and theaverage test result is to be used for acceptance purposes. It isassumed that the contractor can control the density of themixture with a standard deviation of 0.02 g/cm3.X3.2 Precision statement for Test Method D2726 is in TableX3.1.X3.3 The combined standard deviation of the measureddensity:σx5=~0.200210.02692! (X3.1)50.0335 g/cm3X3.4 The standard deviation of the mean of five test results:σx¯5 ~0.0335 / = 5 ! (X3.2)50.0150 g/cm3X3.5 Specification limit using a 95 % confidence interval:Minimum average measured density (X3.3)5 2.365 2 Zα~0.015!5 2.365 2 1.65 ~0.115!35 2.340 g/cmX3.6 With this specification, a contractor who compacts theasphalt mixture to an average density of 2.356 g/cm3wouldmeet the specification 95 % of the time.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or service@astm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http://www.copyright.com/TABLE X3.1 Precision Statement ValuesStandardDeviationAcceptable Range ofTwo Test ResultsSingle-OperatorPrecision0.0124 0.035Multi-OperatorPrecision0.0269 0.076D6607 − 00 (2015)3