1、Designation: E3009 151Standard Test Method forSensory AnalysisTetrad Test1This standard is issued under the fixed designation E3009; 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
2、 indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1NOTEEditorially corrected Table A1.1 in May 2016.1. Scope1.1 This test method covers a procedure for determiningwhether a perceptible sensory difference exists between
3、samples of two products or to estimate the magnitude of theperceptible difference.1.2 This test method applies whether a difference may existin a single sensory attribute or in several.1.3 This test method is applicable when the nature of thedifference between the samples is unknown. The attribute(s
4、)responsible for the difference are not identified.1.4 The tetrad test is more efficient statistically than thetriangle test (Test Method E1885) or the duo-trio test (TestMethod E2610).1.5 The tetrad method involves the evaluation of foursamples. When the products being tested cause excessivesensory
5、 fatigue, carryover, or adaptation, methods that involvethe evaluation of fewer samples (same-different, triangle test,etc.) may be preferred.1.6 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
6、 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:2E253 Terminology Relating to Sensory Evaluation of Mate-rials and ProductsE456 Terminology Relating to Quality and StatisticsE1871
7、 Guide for Serving Protocol for Sensory Evaluation ofFoods and BeveragesE1885 Test Method for Sensory AnalysisTriangle TestE2262 Practice for Estimating Thurstonian Discriminal Dis-tancesE2610 Test Method for Sensory AnalysisDuo-Trio Test2.2 ISO Standards:3ISO 4120 Sensory Analysis Methodology Trian
8、gle TestISO 10399 Sensory Analysis Methodology Duo-TrioTest3. Terminology3.1 DefinitionsFor definition of terms relating to sensoryanalysis, see Terminology E253, and for terms relating tostatistics, see Terminology E456.3.2 Definitions of Terms Specific to This Standard:3.2.1 (alpha) riskprobabilit
9、y of concluding that a per-ceptible difference exists when, in reality, one does not.3.2.1.1 DiscussionAlso known as Type I Error or signifi-cance level.3.2.2 (beta) riskprobability of concluding that no per-ceptible difference exists when, in reality, one does.3.2.2.1 DiscussionAlso known as Type I
10、I Error.3.2.3 Thurstonian measure of sensory difference (effectsize) relative to perceptual noise (standard deviation) (seePractice E2262).3.2.4 productmaterial to be evaluated.3.2.5 sampleunit of product prepared, presented, andevaluated in the test.3.2.6 sensitivitygeneral term used to summarize t
11、he per-formance characteristics of the test; the sensitivity of the test isrigorously defined, in statistical terms, by the values selectedfor , , and .4. Summary of Test Method4.1 Clearly define the test objective in writing.4.2 Choose the number of assessors based on the level ofsensitivity desire
12、d for the test. The sensitivity of the test is, inpart, a function of two competing risks: the risk of declaring1This test method is under the jurisdiction of ASTM Committee E18 on SensoryEvaluation and is the direct responsibility of Subcommittee E18.04 on Fundamen-tals of Sensory.Current edition a
13、pproved May 1, 2015. Published June 2015. DOI: 10.1520/E3009-15E01.2For 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 we
14、bsite.3Available from International Organization for Standardization (ISO), 1, ch. dela Voie-Creuse, CP 56, CH-1211 Geneva 20, Switzerland, http:/www.iso.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1the samples different when t
15、hey are not (that is, -risk) and therisk of not declaring the samples different when they are (thatis, -risk). Acceptable values of and vary depending on thetest objective and should be determined before the test (see forexample Appendix X1).4.3 Each assessor receives four coded samples where twosam
16、ples are of one product and the other two samples are of theother product being tested. The assessors are instructed togroup the four samples into two pairs based on the level ofsimilarity between samples.4.4 Results are tallied and significance determined by ref-erence to a statistical table.5. Sig
17、nificance and Use5.1 The test method is effective for the following testobjectives:5.1.1 To determine whether a perceptible difference resultsor a perceptible difference does not result, for example, whena change is made in ingredients, processing, packaging,handling, or storage; or5.1.2 To select,
18、train, and monitor assessors.5.2 The test method itself does not change whether thepurpose of the test is to determine that two products areperceptibly different versus that the products are not percepti-bly different. Only the selected values of , , and change. Ifthe objective of the test is to det
19、ermine if the two products aresufficiently similar to be used interchangeably, then the valueselected for is typically smaller than the value selected for and the value of is selected to define “sufficiently similar.”6. Apparatus6.1 Carry out the test under conditions that prevent contactbetween ass
20、essors until the evaluations have been completed,for example, using booths that comply with STP 913 (1).46.2 Sample preparation and serving sizes should complywith Practice E1871. See Refs (2) or (3).7. Assessors7.1 All assessors must be familiar with the mechanics of thetetrad test (the format, the
21、 task, and the procedure of evalua-tion). Experience and familiarity with the product and testmethod may increase the sensitivity of an assessor and maytherefore increase the likelihood of finding a significant differ-ence. Monitoring the performance of assessors over time maybe useful.7.2 Choose as
22、sessors in accordance with test objectives. Forexample, if the project results are to represent the generalconsumer population, assessors with unknown sensitivitymight be selected. To increase protection of product quality,assessors with demonstrated acuity should be selected.7.3 The decision to use
23、 trained or untrained assessors shouldbe addressed prior to testing. Training may include a prelimi-nary presentation on the nature of the samples and the problemconcerned. If the test concerns the detection of a particulartaint, consider the inclusion of samples during training thatdemonstrate its
24、presence and absence. Such demonstration willincrease the panels acuity for the taint but may detract fromother differences. See STP 758 for details (4). Allow adequatetime between the exposure to the training samples and theactual tetrad test to avoid carryover.7.4 During the test sessions, avoid g
25、iving information aboutproduct identity, expected treatment effects, or individualperformance until all testing is complete.7.5 Avoid replicate evaluations by the same assessor when-ever possible. However, if replications are needed to produce asufficient number of total evaluations, every effort sh
26、ould bemade to have each assessor perform the same number ofreplicate evaluations.8. Number of Assessors8.1 Choose the number of assessors to yield the level ofsensitivity called for by the test objectives. The sensitivity ofthe test is a function of three values: the -risk, and the -risk,and the ma
27、ximum allowable sensory difference, .8.2 Prior to conducting the test, select values for , , and .The following can be considered as general guidelines.8.2.1 For -risk: A statistically significant result at:8.2.1.1 10 to 5 % (0.10 to 0.05) indicates “slight” evidencethat a difference was apparent;8.
28、2.1.2 5 to 1 % (0.05 to 0.01) indicates “moderate” evi-dence that a difference was apparent;8.2.1.3 1 to 0.1 % (0.01 to 0.001) indicates “strong” evi-dence that a difference was apparent; and8.2.1.4 Below 0.1 % ( 1 represent large values.8.3 Having defined the required level of sensitivity for thete
29、st using 8.2, use Table A1.1 to determine the number ofassessors necessary. Enter Table A1.1 in the section corre-sponding to the selected value of and the column correspond-ing to the selected value of . The minimum required numberof assessors is found in the row corresponding to the selectedvalue
30、of . Alternatively, Table A1.1 can be used to develop aset of values for , , and that provide acceptable sensitivitywhile maintaining the number of assessors within practicallimits. The approach is presented in detail in Ref (5).8.4 Often in practice, the number of assessors is determinedby material
31、 conditions (for example, duration of theexperiment, number of available assessors, quantity of prod-uct). Increasing the number of assessors increases the likeli-hood of detecting small values of . Thus, one should expect touse larger numbers of assessors when trying to demonstratethat products are
32、 similar compared to when testing for a4The boldface numbers in parentheses refer to a list of references at the end ofthis standard.E3009 1512difference. For comparable sensitivity when testing forsimilarity, 40 to 50 assessors are needed.9. Procedure9.1 Prepare worksheets and scoresheets (see Appe
33、ndix X1)in advance of the test so as to utilize an equal number of the sixpossible sequences of two products, A and B:AABB BBAAABAB BABAABBA BAABDistribute these at random among the assessors so thatserving order is balanced.9.2 Present each set of four samples simultaneously ifpossible, following t
34、he same spatial arrangement for eachassessor. Within the set of four samples, assessors are typicallyallowed to make repeated evaluations of each sample asdesired. If the conditions of the test require the prevention ofrepeat evaluations for example, if samples are bulky or leavean aftertaste, prese
35、nt the samples sequentially and do not allowrepeated evaluations. In addition, if the samples change overtime, for example, cereal with milk, samples should be testedsequentially.9.3 Instruct the assessors to evaluate the four test samples inthe order presented. The assessor should then group the fo
36、ursamples into two groups of two based on similarity. It is criticalthat the instructions to the assessors say, “Group the foursamples into two groups of two based on similarity,” and not,“Identify the two samples that are most similar to each other.”The latter wording does not correctly represent t
37、he tetrad taskthe assessor is to perform.9.4 Each scoresheet should provide for a single group ofsamples. If a different set of products is to be evaluated by anassessor in a single session, the completed scoresheet and anyremaining product from the evaluation just completed shouldbe returned to the
38、 test administrator prior to receiving thesubsequent set of test samples. The assessor cannot go back toany of the previous samples or change the verdict on anyprevious test.9.5 Do not ask questions about preference, acceptance, ordegree of difference after the initial grouping of samples intopairs.
39、 The selection the assessor has just made may bias thereply to any additional questions. Responses to such questionsmay be obtained through separate tests for preference,acceptance, degree of difference, etc. (see Manual 26) (6).Acomment section asking why the choice was made may beincluded for the
40、assessors remarks.9.6 The tetrad test is a forced-choice procedure; assessorsare not allowed the option of reporting “no difference.” Anassessor who detects no difference between the samples andrequests to report “no difference,” should be instructed togroup the test samples into two pairs randomly.
41、 In suchsituations the assessor can indicate that the selection was onlya guess in the comments section of the scoresheet.10. Analysis and Interpretation of Results10.1 Use Table A1.2 to analyze the data obtained from atetrad test. The actual number of assessors can be greater thanthe minimum value
42、given in Table A1.1. If the number ofcorrect responses is greater than or equal to the number givenin Table A1.2, conclude that a perceptible difference existsbetween the samples. If the number of correct answers is lessthan the number given in TableA1.2, conclude that the samplesare sufficiently si
43、milar. Again, the conclusions are based on therisks accepted when the level of sensitivity (that is, , , and )was selected in determining the number of assessors (TableA1.1).10.2 If desired, calculate a confidence interval on thesensory difference. This method is described in Appendix X1.11. Report1
44、1.1 Report the test objective, the results, and the conclu-sions. The following additional information is recommended:11.1.1 The purpose of the test and the nature of thetreatment studied;11.1.2 Full Identification of the SamplesOrigin, age, lotnumber, packaging, where obtained, method of preparatio
45、n,quantity, shape, storage prior to testing, serving size, tempera-ture. (Sample information should communicate that all storage,handling, and preparation was done in such a way as to yieldsamples that differ only due to the variable of interest, if at all);11.1.3 The number of assessors, the number
46、 of correctselections, and the result of the statistical evaluation;11.1.4 AssessorsAge, gender, experience in sensorytesting, experience with the product category, experience withthe samples in the test;11.1.5 Any information and any specific instructions giventhe assessor in connection with the te
47、st;11.1.6 The test environment: use of booths, simultaneous orsequential presentation, light conditions, whether the identityof the samples was disclosed after the test, and the manner inwhich is was done; and11.1.7 The location and date of the test and the name of thepanel leader.12. Precision and
48、Bias12.1 Because results of sensory difference tests are func-tions of individual sensitivities, a general statement regardingthe precision of results that is applicable to all populations ofassessors cannot be made. However, adherence to the recom-mendations stated in this standard should increase
49、the repro-ducibility of results and minimize bias.13. Keywords13.1 difference testing; discrimination test; sensory analy-sis; similarity testing; tetrad testE3009 1513ANNEX(Mandatory Information)A1. NUMBER OF ASSESSORS AND CORRECT RESPONSES NEEDED FOR A TETRAD TESTA1.1 See Table A1.1 and Table A1.2.TABLE A1.1 Number of Assessors Needed for Tetrad Test (1)NOTE 1Entries are the minimum number of assessors required to execute a Tetrad test with a pre-specified level of sensitivity determined by thevalues chosen f
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