ASTM_E_2139_-_05_2011.pdf

Designation:E213905(Reapproved 2011)Standard Test Method forSame-Different Test1This standard is issued under the fixed designation E2139;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 test method describes a procedure for comparingtwo products.1.2 This test method does not describe the Thurstonianmodeling approach to this test.1.3 This test method is sometimes referred to as the simple-difference test.1.4 A same-different test determines whether two productsare perceived to be the same or different overall.1.5 The procedure of the test described in this test methodconsists of presenting a single pair of samples to each assessor.The presentation of multiple pairs would require differentstatistical treatment and it is outside of the scope of this testmethod.1.6 This test method is not attribute-specific,unlike thedirectional difference test.1.7 This test method is not intended to determine themagnitude of the difference;however,statistical methods maybe used to estimate the size of the difference.1.8 This test method may be chosen over the triangle orduo-trio tests where sensory fatigue or carry-over are aconcern,or where a simpler task is needed.1.9 This standard may involve hazardous materials,operations,and equipment.This standard does not purport toaddress all of the safety concerns,if any,associated with itsuse.It is the responsibility of the user of this standard toestablish appropriate safety and health practices and deter-mine the applicability of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2E253 Terminology Relating to Sensory Evaluation of Mate-rials and ProductsE456 Terminology Relating to Quality and StatisticsE1871 Guide for Serving Protocol for Sensory Evaluation ofFoods and Beverages2.2 ASTM Publications:2Manual 26 Sensory Testing Methods,2nd EditionSTP 758 Guidelines for the Selection and Training of Sen-sory Panel MembersSTP 913 Guidelines for Physical Requirements for SensoryEvaluation Laboratories2.3 ISO Standard:3ISO 5495 Sensory AnalysisMethodologyPaired Com-parison3.Terminology3.1 For definition of terms relating to sensory analysis,seeTerminology E253,and for terms relating to statistics,seeTerminology E456.3.2 Definitions of Terms Specific to This Standard:3.2.1 (alpha)riskprobability of concluding that a per-ceptible difference exists when,in reality,one does not(alsoknown as Type I Error or significance level).3.2.2 (beta)riskprobability of concluding that no per-ceptible difference exists when,in reality,one does(alsoknown as Type II Error).3.2.3 chi-square teststatistical test used to test hypotheseson frequency counts and proportions.3.2.4 (delta)test sensitivity parameter established priorto testing and used along with the selected values of,andan estimated value of p1to determine the number of assessorsneeded in a study.Delta()is the minimum difference inproportions that the researcher wants to detect,where thedifference is =p2 p1.is not a standard measure ofsensory difference.The same value of may correspond todifferent sensory differences for different values of p1(see 9.5for an example).3.2.5 Fishers Exact Test(FET)statistical test of the equal-ity of two independent binomial proportions.1This test method is under the jurisdiction ofASTM Committee E18 on SensoryEvaluation and is the direct responsibility of Subcommittee E18.04 on Fundamen-tals of Sensory.Current edition approved Aug.1,2011.Published August 2011.Originallyapproved in 2005.Last previous edition approved in 2005 as E213905.DOI:10.1520/E2139-05R11.2For 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.3Available from American National Standards Institute(ANSI),25 W.43rd St.,4th Floor,New York,NY 10036,http:/www.ansi.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 3.2.6 p1proportion of assessors in the population whowould respond different to the matched sample pair.Based onexperience with using the same-different test and possibly withthe same type of products,the user may have a prioriknowledge about the value of p1.3.2.7 p2proportion of assessors in the population whowould respond different to the unmatched sample pair.3.2.8 power 1-(beta)riskprobability of concluding thata perceptible difference exists when,in reality,one of size does.3.2.9 productmaterial to be evaluated.3.2.10 sampleunit of product prepared,presented,andevaluated in the test.3.2.11 sensitivityterm used to summarize the performancecharacteristics of this test.The sensitivity of the test is definedby the four val