ASTM E2263-12(2018)

Standard Test Method for Paired Preference Test

SIGNIFICANCE AND USE
5.1 The paired preference test determines whether or not there is a preference for one product over another product among a specific target population. Knowledge of consumer segments, brand loyalties, the range of product offerings in the marketplace, and the decision risk must be understood when planning a paired preference test.  
5.2 The paired preference method is commonly used in tests with one or more of the following objectives: (1) to establish superiority in preference versus the competition for advertising claims support; (2) to establish the preference of a new product for launch versus a competitor's product; (3) to establish the preference of a reformulated product in a product improvement or product modification project (for example, process change or ingredient change); and (4) to establish the preference of a cost improved product versus the current formulation in a cost savings project. Selected values of Pmax, α, and β will change with all four types of test objectives. These should be selected prior to determination of N.  
5.2.1 Preference versus Competition or Launching a New Product versus Competition—Select a Pmax  to represent what you expect a reasonable preference split to be. The main risk to avoid is to wrongly claim your product is preferred over the competitors. Thus, low values of α are selected, for example, 0.05, 0.01, or 0.001. The desired outcome of this test is to reject the null hypothesis. The alternative hypothesis is one sided: A new or improved product (A) is preferred over the competitor’s product (B). The test is one-sided. The value of β will be determined by the sample size chosen and the size of the preference in the consumer segment selected for the test. Selection of the appropriate number of respondents is determined by Pmax, α, and β, as well as the market segment that must be included in the test (for issues specific to conducting a paired preference test for an advertising claim, refer to Guide E1958).  
5.2.2 C...
SCOPE
1.1 This document covers a procedure for determining preference between two products using either a two-alternative forced-choice task, or with the option of choosing no preference. Preference testing is a type of hedonic testing.  
1.2 A paired preference test determines whether there is a statistically significant preference between two products for a given population of respondents. The target population must be carefully considered.  
1.3 This method establishes preference in a single evaluation context. Replicated tests will not be covered within the scope of this document.  
1.4 Paired preference testing can address overall preference or preference for a specified sensory attribute.  
1.5 The method does not directly determine the magnitude of preference.  
1.6 This method does not address whether or not two samples are perceived as different. Refer to Test Method E2164 for directional difference test.  
1.7 A paired preference test is a simple task for respondents, and can be used with populations that have minimal reading or comprehension 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 respondents' affective or hedonic response. It differs from paired comparison testing which measures objective characteristics of the product. Preference results are always dependent on the population sampled.  
1.9 This standard does not purport to address all of the safety problems associated with its use, when testing includes hazardous materials, operations, or equipment. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and to determine the applicability of regulatory limitations prior to use.  
1.10 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles fo...

General Information

• Status: Published
• Publication Date: 31-Jul-2018
• ICS: 03.100.10 - Purchasing. Procurement. Logistics
• Technical Committee: E18 - Sensory Evaluation
• Drafting Committee: E18.04 - Test Methods

Relations

• Replaces: ASTM E2263-12 - Standard Test Method for Paired Preference Test
• Effective Date: 01-Aug-2018
• Refers: ASTM E456-13a(2022)e1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Apr-2022
• Refers: ASTM E253-19 - Standard Terminology Relating to Sensory Evaluation of Materials and Products
• Effective Date: 15-Oct-2019
• Refers: ASTM E1958-19a - Standard Guide for Sensory Claim Substantiation
• Effective Date: 01-Aug-2019
• Refers: ASTM E1958-19 - Standard Guide for Sensory Claim Substantiation
• Effective Date: 01-Mar-2019
• Refers: ASTM E253-18a - Standard Terminology Relating to Sensory Evaluation of Materials and Products
• Effective Date: 01-Oct-2018
• Refers: ASTM E253-18 - Standard Terminology Relating to Sensory Evaluation of Materials and Products
• Effective Date: 15-Jun-2018
• Refers: ASTM E1958-18 - Standard Guide for Sensory Claim Substantiation
• Effective Date: 01-Jun-2018
• Refers: ASTM E456-13A(2017)e1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Oct-2017
• Refers: ASTM E456-13A(2017)e3 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Oct-2017
• Refers: ASTM E1871-17 - Standard Guide for Serving Protocol for Sensory Evaluation of Foods and Beverages
• Effective Date: 01-Sep-2017
• Refers: ASTM E253-17 - Standard Terminology Relating to Sensory Evaluation of Materials and Products
• Effective Date: 01-May-2017
• Refers: ASTM E1958-16a - Standard Guide for Sensory Claim Substantiation
• Effective Date: 01-Oct-2016
• Refers: ASTM E2164-16 - Standard Test Method for Directional Difference Test
• Effective Date: 01-Oct-2016
• Refers: ASTM E1958-16 - Standard Guide for Sensory Claim Substantiation
• Effective Date: 01-Aug-2016

Overview

ASTM E2263-12(2018): Standard Test Method for Paired Preference Test offers a scientifically robust procedure for determining consumer preference between two products within a specific target population. As an ASTM International standard, it is widely recognized for its clarity and reliability, supporting industries that rely on sensory evaluations for product development, competitive analysis, and marketing claims. This method involves presenting participants with a paired comparison, using either a forced-choice task or with an option for no preference, to establish statistically significant product preferences.

Key Topics

• Purpose and Scope

  • Evaluates whether a statistically significant preference exists between two products in a defined population.
  • Applicable in both forced-choice scenarios and cases allowing a "no preference" response.
  • Focuses on subjective measures of consumer liking (hedonic testing), not objective differences or the magnitude of preference.

• Methodology

  • Respondents are selected based on precise demographics to match the business objective (e.g. current users, target market).
  • Paired samples are served in randomized, coded order to minimize bias.
  • The test can be conducted in central location testing (CLT) or in-home use tests (IHUT).
  • Analysis considers sample size, statistical significance (alpha and beta risks), and sensitivity to ensure credible results.
  • Designed for simplicity, suitable even for populations with minimal reading skills.

• Statistical Considerations

  • Requires careful selection of test sensitivity parameters:
    • α-risk (Type I error): Probability of stating a preference exists when it does not.
    • β-risk (Type II error): Probability of stating there is no preference when one exists.
    • Pmax: Proportion of responses indicating preference, preselected for detecting expected preference ratios.
  • The test may be one-sided (for hypothesized preference direction) or two-sided (no directional assumption), affecting respondent numbers and statistical power.

Applications

• Product Development

  • Assess consumer preference when launching a new product versus an established competitor.
  • Evaluate reforms or improvements (recipe changes, cost-reductions) to ensure ongoing or improved consumer satisfaction.

• Marketing Claims

  • Provide statistically valid evidence of product superiority for substantiating advertising claims.
  • Demonstrate parity in preference to support transitions to alternative formulations or cost-saving ingredients.

• Quality Assurance and Sensory Panels

  • Useful in quality assurance programs to confirm product changes do not negatively affect consumer acceptance.
  • Can be implemented with minimal respondent instruction, suitable for diverse demographic groups.

• Research and Academia

  • Form a foundation for hedonic testing in sensory science research focused on consumer preference studies.

Related Standards

• ASTM E1958 – Guide for Sensory Claim Substantiation: Guidance on using sensory tests for marketing and label claims.
• ASTM E2164 – Test Method for Directional Difference Test: Determines whether two products are perceived as different, not preferred.
• ASTM E253 – Terminology Relating to Sensory Evaluation: Definitions for sensory testing vocabulary.
• ASTM E456 – Terminology Relating to Quality and Statistics: Standardized statistical terminology.
• ASTM E1871 – Guide for Serving Protocol for Sensory Evaluation of Foods and Beverages: Practical procedures for sample handling and presentation.
• ISO 5495 – Sensory Analysis - Methodology - Paired Comparison: International equivalent for paired comparison testing.

Conclusion

ASTM E2263-12(2018) is fundamental for industries leveraging consumer input to drive product innovation, validate sensory improvements, or substantiate marketing statements. Its structured, statistically-sound methodology ensures results are reliable, actionable, and defensible in regulatory or commercial settings, ultimately supporting data-driven product decision-making and competitive differentiation.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E2263 − 12 (Reapproved 2018)
Standard Test Method for
Paired Preference Test
This standard is issued under the fixed designation E2263; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.10 This international standard was developed in accor-
dance with internationally recognized principles on standard-
1.1 This document covers a procedure for determining
ization established in the Decision on Principles for the
preference between two products using either a two-alternative
Development of International Standards, Guides and Recom-
forced-choice task, or with the option of choosing no prefer-
mendations issued by the World Trade Organization Technical
ence. Preference testing is a type of hedonic testing.
Barriers to Trade (TBT) Committee.
1.2 A paired preference test determines whether there is a
2. Referenced Documents
statistically significant preference between two products for a
givenpopulationofrespondents.Thetargetpopulationmustbe 2
2.1 ASTM Standards:
carefully considered.
E253 Terminology Relating to Sensory Evaluation of Mate-
1.3 This method establishes preference in a single evalua- rials and Products
E456 Terminology Relating to Quality and Statistics
tion context. Replicated tests will not be covered within the
scope of this document. E1871 Guide for Serving Protocol for Sensory Evaluation of
Foods and Beverages
1.4 Paired preference testing can address overall preference
E1958 Guide for Sensory Claim Substantiation
or preference for a specified sensory attribute.
E2164 Test Method for Directional Difference Test
1.5 The method does not directly determine the magnitude
2.2 ISO Standard:
of preference.
ISO 5495 Sensory Analysis—Methodology—Paired Com-
parison
1.6 This method does not address whether or not two
samplesareperceivedasdifferent.RefertoTestMethodE2164
3. Terminology
for directional difference test.
3.1 For definition of terms relating to sensory analysis, see
1.7 Apairedpreferencetestisasimpletaskforrespondents,
Terminology E253, and for terms relating to statistics, see
and can be used with populations that have minimal reading or
Terminology E456.
comprehension skills, or both.
3.2 Definitions of Terms Specific to This Standard:
1.8 Preference is not an intrinsic attribute of the product,
3.2.1 α (alpha) risk—the probability of concluding that a
such as hue is, but is a subjective measure relating to
preference exists when, in reality, one does not. (Also known
respondents’ affective or hedonic response. It differs from
as Type I Error or significance level.)
paired comparison testing which measures objective character-
3.2.2 β (beta) risk—the probability of concluding that no
istics of the product. Preference results are always dependent
preference exists when, in reality, one does. (Also known as
on the population sampled.
Type II Error.)
1.9 This standard does not purport to address all of the
3.2.3 common responses—for a one-sided test, the number
safety problems associated with its use, when testing includes
of respondents selecting the product that is expected to be
hazardous materials, operations, or equipment. It is the re-
preferred. For a two-sided test, the largest number of respon-
sponsibility of the user of this standard to establish appropriate
dents selecting either product.
safety, health, and environmental practices and to determine
the applicability of regulatory limitations prior to use.
3.2.4 one-sided test—a test in which the researcher has an a
priori assumption concerning the direction of the preference.
1 2
This test method is under the jurisdiction ofASTM Committee E18 on Sensory For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Evaluation and is the direct responsibility of Subcommittee E18.04 on Fundamen- contactASTM Customer Service at [e-mail]. ForAnnual Book ofASTM
tals of Sensory. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Aug. 1, 2018. Published August 2018. Originally theASTM website.
approved in 2004. Last previous edition approved in 2012 as E2263 – 12. DOI: Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
10.1520/E2263-12R18. 4th Floor, New York, NY 10036.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2263 − 12 (2018)
In this case, the alternative hypothesis will express that a 4.4 Results are tallied and significance determined by ref-
specific product is preferred over another product (that is only, erence to a statistical table (or calculation).
A > B or A < B), depending on the a priori belief.
4.5 Testingisgenerallyconductedforonepairofsamplesto
3.2.5 two-sided test—a test in which the researcher does not
avoid bias from one set of samples to another.
have any a priori assumption concerning direction of the
preference. In this case, the alternative hypothesis is that the
5. Significance and Use
two products are not equally preferred (that is, A ≠ B).
5.1 The paired preference test determines whether or not
3.2.6 P — a test sensitivity parameter established prior to
max there is a preference for one product over another product
testing and used along with the selected values of α and β to
among a specific target population. Knowledge of consumer
determinethenumberofrespondentsneededinastudy. P is
max segments, brand loyalties, the range of product offerings in the
the proportion of common responses that the researcher wants
marketplace, and the decision risk must be understood when
the test to be able to detect with a probability of 1-β. For
planning a paired preference test.
example, if a researcher wants to have a 90 % confidence level
5.2 Thepairedpreferencemethodiscommonlyusedintests
of detecting a 60:40 split in preference, then P = 60 % and
max
with one or more of the following objectives: (1) to establish
β = 0.10.
superiority in preference versus the competition for advertising
3.2.7 sensitivity—a general term used to summarize the
claims support; (2) to establish the preference of a new product
performance characteristics of the paired preference test. The
for launch versus a competitor’s product; (3) to establish the
sensitivity of the test is defined, in statistical terms, by the
preferenceofareformulatedproductinaproductimprovement
values selected for α, β, and P . Smaller values of α, β, and
max
or product modification project (for example, process change
P indicate a more sensitive test.
max
or ingredient change); and (4) to establish the preference of a
3.2.8 p —the proportion of common responses which is cost improved product versus the current formulation in a cost
c
savings project. Selected values of P , α, and β will change
calculated from the test data.
max
with all four types of test objectives. These should be selected
3.2.9 product—the material from which samples are se-
prior to determination of N.
lected.
5.2.1 Preference versus Competition or Launching a New
3.2.10 sample—the unit of product prepared, presented, and
Product versus Competition—Select a P to represent what
max
evaluated in the test.
youexpectareasonablepreferencesplittobe.Themainriskto
3.2.11 respondent—also known as assessor; a general term avoid is to wrongly claim your product is preferred over the
for any individual responding to stimuli in a sensory test. competitors. Thus, low values of α are selected, for example,
Trained panelists or experienced discrimination panelists do 0.05,0.01,or0.001.Thedesiredoutcomeofthistestistoreject
not serve as respondents in a paired preference test. the null hypothesis. The alternative hypothesis is one sided: A
neworimprovedproduct(A)ispreferredoverthecompetitor’s
product (B). The test is one-sided. The value of β will be
4. Summary of Test Method
determined by the sample size chosen and the size of the
4.1 Clearly define the test objective in writing, specifying
preference in the consumer segment selected for the test.
the type of audience or population you wish to recruit as
Selection of the appropriate number of respondents is deter-
respondents. (If objective involves substantiating an advertis-
mined by P , α, and β, as well as the market segment that
max
ing claim, refer to Guide E1958.)
must be included in the test (for issues specific to conducting
4.2 Choose the number of respondents (N) to be recruited
a paired preference test for an advertising claim, refer to Guide
based on the sensitivity level desired for the test (P , α, and
E1958).
max
β). The sensitivity of the test is, in part, a function of two
5.2.2 Cost Reduction or Reformulation of an Existing
competing risks—the risk of declaring a preference when there
Product—When parity preference is the desired test outcome,
is none (that is, α-risk) and the risk of not declaring that a
values of α are increased and values of β are decreased. For
preference exists when there is a preference (that is, β-risk).
example, if a product is developed which represents a signifi-
Acceptable values of α and β vary depending on the test
cant cost savings over the current formulation and there is
objective. The values should be agreed upon by all parties
concern over alienation of current users,α might be selected at
affected by the results of the test before the test is conducted.
0.20 and β might be selected at 0.01. Parity testing can be
either one-or two-sided depending on the action standards of
4.3 In paired preference testing, an assessor receives a pair
the test. The test is one-sided if the action standard is that the
of coded samples that are identified with appropriate non-
product must be parity or better. The test is two-sided if the
biasing codes. The assessor is asked to choose the sample that
action standard is parity only. The number of respondents
is preferred.
chosen must reflect the risk of replacing the current product
4.3.1 When using a forced choice procedure, a sample must
with the cost-reduced product.
be chosen even if the selection is based only on a random
selection by the assessor.
5.3 Atest result of superiority or parity does not ensure that
4.3.2 If a choice is not forced, a “no preference” option the test conclusion is correct. An incorrect test result can be
should be included, and the data must be handled in a different obtained when the sample of respondents is selected in a way
way. that does not reflect the true preference in the population of
E2263 − 12 (2018)
interest, or when the number of respondents is too small to 8.1.2 Whentheresearcherwantstotakeonlyasmallchance
correctly reflect the preference status of the two products of concluding that a preference exists when it does not (for
among the target consumer group. Careful selection of P ,α, example, when testing to support a claim of superiority), the
max
and β and an appropriate selection of respondents is needed to most commonly used values for α-risk and β-risk are α = 0.05
minimize the risk of drawing an incorrect conclusion in and β = 0.20. These values can be adjusted on a case-by-case
forced-choice paired preference testing. basis to reflect the sensitivity desired versus the number of
respondents available. When testing for a preference with a
6. Apparatus
limited number of respondents, hold the α-risk at a relatively
small value and allow the β-risk to increase in order to control
6.1 Carry out the test under conditions that prevent contact
the risk of falsely concluding that a preference is present.
between respondents until the evaluations have been com-
8.1.3 Whentheresearcherwantstotakeonlyasmallchance
pleted.
of missing a preference that exists (for example, when testing
6.2 Sample preparation and serving sizes should comply
to support a claim of parity preference), the most commonly
with Practice E1871, or see Herz and Cupchik or Todrank et
used values for α-risk and β-risk are α = 0.20 and β = 0.05.
al.
These values can be adjusted on a case-by-case basis to reflect
the sensitivity desired versus the number of respondents
7. Respondents
available. When testing for parity with a limited number of
7.1 Choose the appropriate set of respondents on the basis
respondents, hold the β-risk at a relatively small value and
of the test objective. Selecting the appropriate set of assessors
allow the α-risk to increase in order to control the risk of
for a preference test is critical since preference responses vary
missing a preference that truly exists.
depending on the consumer group targeted. The most appro-
8.1.4 For P , the proportion of common responses falls
max
priate respondents to determine product preference are the
into three ranges: (1) P < 55 % represents “small” values;
max
current or potential consumers of the product category.
(2)55%≤ P ≤65 %represents“mediumsized”values;and
max
7.2 Respondents must be selected based upon the objective (3) P > 65 % represents “large” values.
max
ofthestudyandaredependentonthebusinessimplication.For
8.2 Having defined the required sensitivity for the test using
a new product, the respondents should represent target con-
8.1, use Table X1.1 to determine the number of respondents
sumers.Foranexistingproduct,respondentsmayincludeusers
necessary for a one-sided test, or Table X2.1 to determine the
of the product. If your business objective is to ensure that
number of respondents necessary for two-sided test. Select the
market share is not lost when making formula changes,
section of the table corresponding to the selected P value
max
respondents should include heavy category or product users.
and the column corresponding to the selected β value. The
minimum required number of respondents is found in the row
8. Number of Respondents
corresponding to the selected value of α. Alternatively, Table
8.1 Once the target population has been clearly defined,
X1.1 can be used to develop a set of values for P , α, and β
max
choose the number of respondents required for the test as
that provide acceptable sensitivity while maintaining the num-
follows:(1)firstdetermineifthetestisone-sidedortwo-sided,
ber of respondents within practical limits.
and (2) establish the sensitivity required by the test objectives
8.2.1 Using the parameters: α = 0.05, β = 0.20, and P =
max
by selecting values for the three test-sensitivity parameters: the
60 %, the researcher would use the section of Table X1.1
α-risk, the β-risk, and the maximum allowable proportion of
correspondingto P =60 %andthecolumncorrespondingto
max
common responses, P , that would represent a meaningful
max
β = 0.20. In the row corresponding to α = 0.05, it is found that
departure from parity (50:50) preference as decided by the
158 respondents will be needed for the test.
research team.
8.3 Often in practice, the number of respondents is deter-
8.1.1 The test is one-sided if the researcher has an a priori
mined by project constraints (for example, duration of the
interest in only one of the samples being preferred. For
experiment, number of respondents available, quantity of
example, the test is one-sided if the researcher wants to
sample, budgetary constraints). The power of the test should
determine if the product is preferred to the major competitor’s
then be computed. For this purpose, the following parameters
product. The test is two-sided if the researcher has no a priori
need to be defined: α, observed P , and the number of
max
assumption in a particular sample being preferred. For
respondents, n.The observed P corresponds to the observed
max
example, the test is two-sided if two prototype samples are
proportion of common responses, n is determined by the test
being compared and the researcher wants to establish if one
realization, and α should be fixed by the experimenter prior to
sample is preferred over the other sample. More respondents
thetestbeingconducted.Withthisinformation,anexactpower
are needed for a two-sided test than for a one-sided test (see
computation can be achieved using appropriate software.
5.2.1 and 5.2.2).
However, an approximate value can already be inferred by
reverse lookup using Table X1.1 or Table X2.1, depending on
whetherthealternativeisone-ortwo-sided.First,usethevalue
Herz, R. S. and Cupchik, G. C., “An Experimental Characterization of
Odor-evoked Memories in Humans,” Chemical Senses, Vol 17, No. 5, 1992, pp.
of P closest to the observed one to select a group of rows,
max
519-528.
then select among these rows the one corresponding to the
Todrank, J., Wysocki, C. J., and Beauchamp, G. K., “The Effects ofAdaptation
selected value of α. Finally, select the cell having the number
on the Perception of Similar and Dissimilar Odors,” Chemical Senses, Vol 16, No.
5, 1991, pp. 476-482. of assessors closest to the actual number of assessors. The
E2263 − 12 (2018)
correspondingcolumnheadingwillgiveacloseestimateofthe 10. Analysis and Interpretation of Results
actual power of the test (1-β). Lower sample sizes will reduce
10.1 The procedure used to analyze the results of a paired
the power of the test.
preference test depends on whether or not a “no preference”
option is allowed.
9. Procedure
10.1.1 If a forced choice procedure is used, analyze as
9.1 Paired preference can be used in either CLT (Central
detailed in 10.2.
Location Test) or IHUT (in-home use test) designs. The
10.1.2 If a “no preference” option is allowed, then there are
following discussion focuses on CLT testing procedures,
various ways to handle the data depending on the test objec-
however, randomizations and data analyses would be similar
tives. Typically the no preference data is split in some manner
for IHUT’s.
between “A” and “B.” Regardless of how the no preference
9.2 Prepare serving order worksheet and ballot in advance
dataarehandled,itisalwaysimportanttoreportthepercentage
of the test to ensure a balanced order of presentation of the two
ofnopreferenceresponsesandtakethoseintoaccountforyour
samples. Balance the serving sequences of the samples (AB
final action steps. (Refer to Guide E1958 for decision rules
and BA) across all respondents. Serving order worksheets
regarding handling of no preference votes and specific claims.)
should also include complete sample identification information
either by product name or coded reference for double blind
10.2 Analysis for Preference—Different analyses are used
studies. See Appendix X1.
depending on whether the number of respondents is equal to or
greater than planned or fewer than planned.
9.3 It is critical to the validity of the test that respondents
cannot differentiate the samples based on the way they are 10.2.1 If the actual number of respondents is equal to or
presented. For example, in a test evaluating flavor differences,
greater than planned, refer to Table X1.2 (one-sided) or Table
one should avoid any subtle differences in temperature or
X2.2(two-sided)toanalyzethedata.Ifthenumberofcommon
appearance caused by factors such as the time sequence of
responses is equal to or greater than the number given in the
preparation. Code the vessels containing the samples in a
table, conclude that there is a preference between the products.
uniform manner, using three digit numbers chosen at random
If the number of common responses is fewer than the number
for each test. Prepare samples out of sight and in an identical
given in the table, conclude that there is no preference. The
manner: same apparatus, same vessels, same quantities of
conclusions, “preference” or “no preference,” are based on the
sample (see Practice E1871, ASTM Serving Protocols).
predetermined α, β, and P levels.
max
9.4 Present the pair of samples simultaneously if possible,
10.2.2 When the number of respondents is fewer than
following the same spatial arrangement for each assessor (on a
planned, then the data analysis is the same as 10.2.1 above.
line to be sampled always from left to right, or from front to
Understand that the β-risk is now larger than the value chosen
back, etc.). Respondents are typically allowed to evaluate each
because a smaller number of respondents participated in the
samplemorethanonce.Iftheconditionsofthesamplesrestrict
test. A result of “no preference” becomes more likely as N
reevaluating the samples (for example, if samples are bulky,
decreases.
leave an aftertaste, or show slight differences in appearance
10.3 Analysis for Parity—Different analyses are used de-
that cannot be masked), present the samples sequentially and
pending on whether the number of respondents is equal to or
do not allow repeated evaluations.
greater than planned or fewer than planned. There is a direct
9.5 It is not recommended that more than the preference
relationship between sample size (N) and test sensitivity in
question be asked about the samples, because the selection the
parity testing.
respondent has made on the initial question may bias the
10.3.1 Whentheactualnumberofrespondentsisequaltoor
response to subsequent questions. Responses to additional
greater than planned, then the analysis is conducted as outlined
questions may be obtained through separate tests for
in 10.2.1.
acceptance, degree of difference, etc. See Manual 26.A
section soliciting open-ended comments may be included
10.3.2 When the number of respondents is fewer than
following the initial preference question.
planned, then data analysis consists of calculating a confidence
interval. A confidence interval is calculated because the α, β,
9.6 Thepairedpreferencetestcaneitherbeforced-choiceor
and P levels are different in parity preference testing. The
have the option of no preference.
max
calculations are as follows, where c = the number of common
9.6.1 When using the paired preference test as a forced-
responses, and n = the total number of respondents:
choice procedure, respondents are not allowed the option of
reporting“nopreference.”Arespondentwhohasnopreference
Proportion of common responses
for either of the samples should be instructed to randomly
P 5 c/n
c
select one of the samples, and can indicate in the comments
S ~standard deviation of P ! 5 =P ~1 2 P !/n
c c c c
section that they had no preference.
Confidence Limit 5 P 6z S
c β c
10.3.3 z is the critical value of the standard normal distri-
β
6 bution. Values of z for some commonly used values of β-risk
β
MNL26-2ND Sensory Testing Methods: Second Edition, Chambers, E. and
Wolf, M.B., Eds., ASTM International, 1996. are:
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