ASTM E2139-05

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:E2139–05
Standard Test Method for
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Same-Different Test
This standard is issued under the fixed designation E2139; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope of Foods and Beverages
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2.2 ASTM Publications:
1.1 This test method describes a procedure for comparing
Manual 26 Sensory Testing Methods, 2nd Edition
two products.
STP 758 Guidelines for the Selection and Training of
1.2 This test method does not describe the Thurstonian
Sensory Panel Members
modeling approach to this test.
STP913 Guidelines for Physical Requirements for Sensory
1.3 This test method is sometimes referred to as the simple-
Evaluation Laboratories
difference test.
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2.3 ISO Standard:
1.4 A same-different test determines whether two products
ISO 5495 Sensory Analysis—Methodology—Paired Com-
are perceived to be the same or different overall.
parison
1.5 The procedure of the test described in this test method
consistsofpresentingasinglepairofsamplestoeachassessor.
3. Terminology
The presentation of multiple pairs would require different
3.1 For definition of terms relating to sensory analysis, see
statistical treatment and it is outside of the scope of this test
Terminology E253, and for terms relating to statistics, see
method.
Terminology E456.
1.6 This test method is not attribute-specific, unlike the
3.2 Definitions of Terms Specific to This Standard:
directional difference test.
3.2.1 a (alpha) risk—probability of concluding that a per-
1.7 This test method is not intended to determine the
ceptible difference exists when, in reality, one does not (also
magnitude of the difference; however, statistical methods may
known as Type I Error or significance level).
be used to estimate the size of the difference.
3.2.2 b (beta) risk—probability of concluding that no per-
1.8 This test method may be chosen over the triangle or
ceptible difference exists when, in reality, one does (also
duo-trio tests where sensory fatigue or carry-over are a
known as Type II Error).
concern, or where a simpler task is needed.
3.2.3 chi-square test—statisticaltestusedtotesthypotheses
1.9 This standard may involve hazardous materials, opera-
on frequency counts and proportions.
tions, and equipment. This standard does not purport to
3.2.4 D (delta)—test sensitivity parameter established prior
address all of the safety concerns, if any, associated with its
to testing and used along with the selected values of a, b, and
use. It is the responsibility of the user of this standard to
an estimated value of p to determine the number of assessors
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establish appropriate safety and health practices and deter-
needed in a study. Delta (D) is the minimum difference in
mine the applicability of regulatory limitations prior to use.
proportions that the researcher wants to detect, where the
2. Referenced Documents difference is D = p − p . D is not a standard measure of
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sensory difference. The same value of D may correspond to
2.1 ASTM Standards:
different sensory differences for different values of p (see 9.5
E253 Terminology Relating to Sensory Evaluation of Ma- 1
for an example).
terials and Products
3.2.5 Fisher’s Exact Test (FET)—statistical test of the
E456 Terminology Relating to Quality and Statistics
equality of two independent binomial proportions.
E1871 Guide for Serving Protocol for Sensory Evaluation
3.2.6 p —proportion of assessors in the population who
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would respond different to the matched sample pair. Based on
experiencewithusingthesame-differenttestandpossiblywith
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ThistestmethodisunderthejurisdictionofASTMCommitteeE18onSensory
the same type of products, the user may have a priori
Evaluation of Materials and Products and is the direct responsibility of Subcom-
knowledge about the value of p .
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mittee E18.04 on Fundamentals of Sensory.
Current edition approved Nov. 1, 2005. Published November 2005. DOI: 3.2.7 p —proportion of assessors in the population who
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10.1520/E2139-05.
would respond different to the unmatched sample pair.
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For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
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E2139–05
3.2.8 power 1-b (beta) risk—probability of concluding that 6.2
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