1、Designation: E2263 04 E2263 12Standard Test Method forPaired Preference Test1This standard is issued under the fixed designation E2263; 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 parenthe
2、ses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This document covers a procedure for determining preference between two products using either a two-alternativeforced-choice, which may or may not includ
3、e forced-choice task, or with the option of choosing no preference. Preference testingis a type of hedonic testing.1.2 A paired preference test determines whether there is a statistically significant preference between two products for a givenpopulation of respondents. The target population must be
4、carefully considered.1.3 This method establishes preference in a single evaluation context. Replicated tests will not be covered within the scope ofthis document.1.4 Paired preference testing can address overall preference or preference for a specified sensory attribute.1.5 The method does not direc
5、tly determine the magnitude of preference.1.6 This method does not address whether or not two samples are perceived as different. See Refer to Test Method E2164. fordirectional difference test.1.7 A paired preference test is a simple task for respondents, and can be used with populations that have m
6、inimal reading orcomprehension skills, or both.1.8 Preference is not an intrinsic attribute of the product, such as hue is, but is a subjective measure relating to respondentsaffective or hedonic response. It differs from paired comparison testing which measures objective characteristics of the prod
7、uct.Preference results are always dependent on the population sampled.1.9 This standard does not purport to address all of the safety concerns, if any, problems associated with its use. use, whentesting includes hazardous materials, operations, or equipment. It is the responsibility of the user of t
8、his standard to establishappropriate safety and health practices and to determine the applicability of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E253 Terminology Relating to Sensory Evaluation of Materials and ProductsE456 Terminology Relating to Quality and Stat
9、isticsE1858 Test Method for Determining Oxidation Induction Time of Hydrocarbons by Differential Scanning CalorimetryE1871 Guide for Serving Protocol for Sensory Evaluation of Foods and BeveragesE1958 Guide for Sensory Claim SubstantiationE2164 Test Method for Directional Difference Test2.2 ASTM Pub
10、lication:Manual 26 Sensory Testing Methods, 2nd Edition22.2 ISO Standard:ISO 5495 Sensory AnalysisMethodologyPaired Comparison31 This test method is under the jurisdiction of ASTM Committee E18 on Sensory Evaluation and is the direct responsibility of Subcommittee E18.04 on Fundamentalsof Sensory.Cu
11、rrent edition approved March 1, 2004Oct. 15, 2012. Published March 2004December 2012. Originally approved in 2004. Last previous edition approved in 2004 asE2263 04. DOI: 10.1520/E2263-04.10.1520/E2263-12.2 For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer
12、 Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036.This document is not an ASTM standard and is
13、 intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the
14、current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13. Terminology3.1 For definition of terms relating to sensory analysis, see Terminology E253
15、, 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 a preference exists when, in reality, one does not. (Also known as TypeI Error or significance level.)3.2.2 (beta) riskthe probability o
16、f concluding that no preference exists when, in reality, one does. (Also known as Type IIError.)3.2.3 common responsesfor a one-sided test, the number of respondents selecting the product that is expected to be preferred.For a two-sided test, the largest number of respondents selecting either produc
17、t.3.2.4 one-sided testa test in which the researcher has an a priori interestassumption concerning the direction of the preference.In this case, the alternative hypothesis will express that a specific product is preferred over another product (that is, is only, A B or A 65 % represents “large” value
18、s.8.1.5 For example, if a researcher is planning a test to support a superior preference claim for a product over the majorcompetitors product, the researcher might choose the following values for the test-sensitivity parameters: = 0.05, = 0.20, andPmax = 60 %. The test is one-sided because the rese
19、archer is only interested in the situation where their product is preferred.8.2 Having defined the required sensitivity for the test using 8.1, use Table X1.1 to determine the number of respondentsnecessary for a one-sided test, or Table X1.2X2.1 to determine the number of respondents necessary for
20、two-sided test. Select thesection of the table corresponding to the selected Pmax value and the column corresponding to the selected value. The minimumrequired number of respondents is found in the row corresponding to the selected value of . Alternatively, Table X1.1 can be usedto develop a set of
21、values for Pmax, , and that provide acceptable sensitivity while maintaining the number of respondents withinpractical limits.8.2.1 Using the valuesparameters: from the example= 0.05, in 8.1.5, the = 0.20, and Pmax = 60 %, the researcher would usethe section of Table X1.1 corresponding to Pmax = 60
22、% and the column corresponding to = 0.20. In the row corresponding to = 0.05, it is found that 158 respondents will be needed for the test.8.3 Often in practice, the number of respondents is determined by project constraints (for example, duration of the experiment,number of available respondents,re
23、spondents available, quantity of sample, budgetary restraints).constraints). The power of the testshould then be computed. For this purpose, the following parameters need to be defined: , observed Pmax, and the number ofrespondents, n. The observed Pmax corresponds to the observed proportion of comm
24、on responses, n is determined by the testrealization, and should be fixed by the experimenter prior to the test conduct. being conducted. With this information, an exactpower computation can be achieved using appropriate software. However, an approximate value can already be inferred by reverselooku
25、p using Table X1.1 or Table X1.2X2.1, depending on whether the alternative is one- or two-sided. First, use the value of Pmaxclosest to the observed one to select a group of rows, then select among these rows the one corresponding to the selected valueof . Finally, select the cell having the number
26、of assessors closest to the actual number of assessors. The corresponding columnheading will give a close estimate of the actual power of the test (1-). Lower sample sizes will reduce the power of the test.9. Procedure9.1 Paired preference can be used in either CLT (Central Location Test) or IHUT (I
27、nhome Use Test)(in-home use test) designs.The following discussion focuses on CLT testing procedures, however, randomizations and data analyses would be similar forIHUTs.9.2 Prepare serving order worksheet and ballot in advance of the test to ensure a balanced order of presentation of the twosamples
28、. Balance the serving sequences of the samples (AB and BA) across all respondents. Serving order worksheets should alsoinclude complete sample identification information either by product name or coded reference for double blind studies. SeeAppendix X1.9.3 It is critical to the validity of the test
29、that respondents cannot differentiate the samples based on the way they are presented.For example, in a test evaluating flavor differences, one should avoid any subtle differences in temperature or appearance causedby factors such as the time sequence of preparation. Code the vessels containing the
30、samples in a uniform manner, using three digitnumbers chosen at random for each test. Prepare samples out of sight and in an identical manner, that is, manner: same apparatus,same vessels, same quantities of sample (see Practice E1871)., ASTM Serving Protocols).9.4 Present the pair of samples simult
31、aneously if possible, following the same spatial arrangement for each assessor (on a lineto be sampled always from left to right, or from front to back, and so forth). etc.). Respondents are typically allowed to tryevaluateeach sample more than once. If the conditions of the samples restrict retryin
32、greevaluating the samples (for example, if samples arebulky, leave an aftertaste, or show slight differences in appearance that cannot be masked), present the samples sequentially anddo not allow repeated evaluations.9.5 It is not recommended that more than one the preference question be asked about
33、 the samples, because the selection theassessorrespondent has made on the initial question may bias the replyresponse to subsequent questions. Responses to additionalquestions may be obtained through separate tests for acceptance, degree of difference, and so forth (see Manual 26).etc. See Manual266
34、. A section soliciting open-ended comments may be included following the initial preference question.9.6 The paired preference test can be either be forced-choice or have the option of no preference.9.6.1 When using the paired preference test as a forced-choice procedure, respondents are not allowed
35、 the option of reporting“no preference.” An assessorA respondent who has no preference for either of the samples should be instructed to randomly selectone of the samples, and can indicate in the comments section that they had no preference.6 MNL26-2ND Sensory Testing Methods: Second Edition, Chambe
36、rs, E. and Wolf, M.B., Eds., ASTM International, 1996.E2263 12410. Analysis and Interpretation of Results10.1 The procedure used to analyze the results of a paired preference test depends on whether or not a “no preference” optionis allowed.10.1.1 If a forced choice procedure is used, analyze as det
37、ailed in 10.2.10.1.2 If a “no preference” option is allowed, then there are various ways to handle the data depending on the test objectives.Typically the no preference data is split in some manner between “A” and “B.” Regardless of how the no preference data isarehandled, it is always important to
38、report the percentage of no preference responses and take those into account for your final actionsteps. (Refer to Guide E1958 for decision rules regarding handling of no preference votes and specific claims.)10.1.2.1 For Ad Claim testing for superiority, “no preference” responses go against your co
39、mpanys product superiority.Therefore, those responses are given to the competitive product.10.1.2.2 For Ad Claim testing for parity, “no preference” responses are arguments against the competitive product superiority.Therefore, those responses are given to your companys product.10.1.2.3 For cost red
40、uction or ingredient/supplier changes, “no preference” responses are split between current and test product.10.1.2.4 For product improvement, “no preference” responses are handled similarly to an ad claim superiority claim and givento the current (not “improved”) product.10.1.2.5 For comparison of f
41、ormulation options, where there is no control or current product, no preference responses are splitequally between the two products. It is important to also report the percentage of no preference responses and take those intoaccount for your final action step.10.2 Analysis for PreferenceDifferent an
42、alyses are used depending on ifwhether the number of respondents is equal to orgreater than planned or fewer than planned.10.2.1 WhenIf the actual number of respondents is equal to or greater than planned, refer to Table X1.3X1.2 (one-tailed)(one-sided) or Table X1.4X2.2 (two-tailed)(two-sided) to a
43、nalyze the data. If the number of common responses is equal to or greaterthan the number given in the table, conclude that there is a preference between the products. If the number of common responsesis fewer than the number given in the table, conclude that there is no preference. The conclusions,
44、“preference“preference” or “nopreference,“no preference,” are based on the predetermined , , and Pmax levels.10.2.2 When the actual number of respondents is fewer than planned, then the data analysis is the same as 10.2.1 above.Understand that the -risk is now larger than the value chosen because a
45、smaller number of respondents participated in the test.A result of “no preference” becomes more likely as N decreases.10.3 Analysis for ParityDifferent analyses are used depending on ifwhether the number of respondents is equal to or greaterthan planned or fewer than planned. There is a direct relat
46、ionship between sample size (N) and test sensitivity in parity testing.10.3.1 When the actual number of respondents is equal to or greater than planned, then the analysis is conducted as outlinedin 10.2.1.10.3.2 When the number of respondents is fewer than planned, then data analysis consists of cal
47、culating a confidence interval.A confidence interval is calculated because the , , and Pmax levels are different in parity preference testing. The calculations areas follows, where c = the number of common responses, and n = the total number of respondents:Proportion of common responsesPc1 5c/nSc st
48、andard deviation of Pc!5=Pc12Pc!/nConfidence Limit5Pc1z ScProportion of common responsesPc 5c/nSc standard deviation of Pc!5=Pc12Pc!/nConfidence Limit5Pc6z Sc10.3.3 z is the critical value of the standard normal distribution. Values of z for some commonly used values of -risk are:-risk z0.50 0.0000.
49、40 0.2530.20 0.8420.10 1.2820.05 1.6450.01 2.3260.001 3.090Given the values chosen for and Pmax, if the confidence limit is less than Pmax, then conclude that there is parity (that is, nomore than Pmax of the population would have a preference at the -level of significance). If the confidence limit is greater than Pmax,then conclude that the products are not at parity. Understand that the -risk is larger than the value chosen when a smaller numberof respondents than planned participate in the test.E2263 12510.4 If desire
