1、Designation: E3009 15Standard 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.1. Scope1.1 This test method covers a procedure for determiningwhether a perceptible sensory difference exists betweensamples of two products or to estimate the magnitud
3、e 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)responsible for the difference are not identified.
4、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 fatigue, carryover, or adaptation, methods that in
5、volvethe 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 to establish appro-priate safety and health practi
6、ces 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 Guide for Serving Protocol for Sensory Evaluation
7、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 Triangle TestISO 10399 Sensory Analysis Methodology Duo-
8、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) riskprobability of concluding that a per-ceptible difference exis
9、ts 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 II Error.3.2.3 Thurstonian measure of sensory differ
10、ence (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 the per-formance characteristics of the test; the se
11、nsitivity 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 desired for the test. The sensitivity of the test is, inp
12、art, a function of two competing risks: the risk of declaringthe samples different when they 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 tes
13、t (see forexample Appendix X1).1This 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 approved May 1, 2015. Published June 2015. DOI: 10.1520/E3009-15.2For referenced A
14、STM 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 International Organization for Standardization (ISO), 1, ch. d
15、ela 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 States14.3 Each assessor receives four coded samples where twosamples are of one product and the other two samples are
16、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. Significance and Use5.1 The test method is effective for
17、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, train, and monitor assessors.5.2 The test method itsel
18、f 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 determine if the two products aresufficiently similar to
19、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 assessors until the evaluations have been completed,for e
20、xample, 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 task, and the procedure of evalua-tion). Experience a
21、nd 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 assessors in accordance with test objectives. Forexample
22、, 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 trained or untrained assessors shouldbe addressed pri
23、or 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 presence and absence. Such demonstration willincrease
24、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 giving information aboutproduct identity, expected trea
25、tment 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 should bemade to have each assessor perform the same num
26、ber 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 maximum allowable sensory difference, .8.2 Prior to cond
27、ucting 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;8.2.1.2 5 to 1 % (0.05 to 0.01) indicates “moderate” evi
28、-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 thetest using 8.2, use Table A1.1 to determine the number o
29、fassessors 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 of . Alternatively, Table A1.1 can be used to develop
30、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 conditions (for example, duration of theexperiment, n
31、umber 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 similar compared to when testing for adifference. For
32、 comparable sensitivity when testing forsimilarity, 40 to 50 assessors are needed.4The boldface numbers in parentheses refer to a list of references at the end ofthis standard.E3009 1529. Procedure9.1 Prepare worksheets and scoresheets (see Appendix X1)in advance of the test so as to utilize an equa
33、l 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 the same spatial arrangement for eachassessor. Within th
34、e 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, present the samples sequentially and do not allowrepeated ev
35、aluations. 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 foursamples into two groups of two based on similarity. I
36、t 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 the tetrad taskthe assessor is to perform.9.4 Each score
37、sheet 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 test administrator prior to receiving thesubsequent se
38、t 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. The selection the assessor has just made may bias ther
39、eply 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 assessors remarks.9.6 The tetrad test is a forced-choic
40、e 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. In suchsituations the assessor can indicate that the s
41、election 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 given in Table A1.1. If the number ofcorrect responses
42、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 similar. Again, the conclusions are based on therisks acc
43、epted 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. Report11.1 Report the test objective, the results, and the con
44、clu-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 preparation,quantity, shape, storage prior to testing, serving si
45、ze, 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 of correctselections, and the result of the statistica
46、l 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 test;11.1.6 The test environment: use of booths, simultan
47、eous 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 Bias12.1 Because results of sensory difference tests ar
48、e 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 the repro-ducibility of results and minimize bias.13. K
49、eywords13.1 difference testing; discrimination test; sensory analy-sis; similarity testing; tetrad testE3009 153ANNEX(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 for , , and . Enter the table in the section corresponding
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