ASTM_E_2164_-_08.pdf

Designation:E216408Standard Test Method forDirectional Difference Test1This standard is issued under the fixed designation E2164;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 covers a procedure for comparing twoproducts using a two-alternative forced-choice task.1.2 This method is sometimes referred to as a pairedcomparison test or as a 2-AFC(alternative forced choice)test.1.3 A directional difference test determines whether a dif-ference exists in the perceived intensity of a specified sensoryattribute between two samples.1.4 Directional difference testing is limited in its applicationto a specified sensory attribute and does not directly determinethe magnitude of the difference for that specific attribute.Assessors must be able to recognize and understand thespecified attribute.Alack of difference in the specified attributedoes not imply that no overall difference exists.1.5 This test method does not address preference.1.6 A directional difference test is a simple task forassessors,and is used when sensory fatigue or carryover is aconcern.The directional difference test does not exhibit thesame level of fatigue,carryover,or adaptation as multiplesample tests such as triangle or duo-trio tests.For detail oncomparisons among the various difference tests,see Ennis(1),MacRae(2),and OMahony and Odbert(3).21.7 The procedure of the test described in this documentconsists of presenting a single pair of samples to the assessors.1.8 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:3E253 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 ISO Standard:ISO 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)riskthe probability of concluding that aperceptible difference exists when,in reality,one does not(alsoknown as type I error or significance level).3.2.2 (beta)riskthe probability of concluding that noperceptible difference exists when,in reality,one does(alsoknown as type II error).3.2.3 one-sided testa test in which the researcher has an apriori expectation concerning the direction of the difference.Inthis case,the alternative hypothesis will express that theperceived intensity of the specified sensory attribute is greater(that is,AB)(or lower(that is,AB)for a product relative tothe other.3.2.4 two-sided testa test in which the researcher does nothave any a priori expectation concerning the direction of thedifference.In this case,the alternative hypothesis will expressthat the perceived intensity of the specified sensory attribute isdifferent from one product to the other(that is,AB).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 March 1,2008.Published April 2008.Originallyapproved in 2001.Last previous edition approved in 2007 as E2164 01(2007).DOI:10.1520/E2164-08.2The boldface numbers in parentheses refer to the list of references at the end ofthis standard.3For 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 3.2.5 common responsesfor a one-sided test,the numberof assessors selecting the sample expected to have a higherintensity of the specified sensory attribute.Common responsescould also be defined in terms of lower intensity of the attributeif it is more relevant.For a two-sided test,the larger number ofassessors selecting sample A or B.3.2.6 PmaxA test sensitivity parameter established prior totesting and used along with the selected values of and todetermine the number of assessors needed in a study.Pmaxisthe proportion of common responses that the researcher wantsthe test to be able to detect with a probability of 1.Forexample,if a researcher wants to be 90%confident ofdetecting a 60:40 split in a directional difference test,then Pmax=60%and =0.10.Pmaxis relative to a population of judge