SIST EN ISO 5495:2007

Sensory analysis - Methodology - Paired comparison test (ISO 5495:2005 and ISO 5495:2005/Cor 1:2006)

This International Standard describes a procedure for determining whether there exists a perceptible sensory difference or a similarity between samples of two products concerning the intensity of a sensory attribute. This test is sometimes also referred to as a directional difference test or a 2-AFC test (Alternative Forced Choice). In fact, the paired comparison test is a forced choice test between two alternatives. The method is applicable whether a difference exists in a single sensory attribute or in several, which means that it enables determination of whether there exists a perceptible difference concerning a given attribute, and the specification of the direction of difference, but it does not give any indication of the extent of that difference. The absence of difference for the attribute under study does not signify that there does not exist any difference between the two products.

Sensorische Analyse - Prüfverfahren - Paarweise Vergleichsprüfung (ISO 5495:2005 und ISO 5495:2005/Cor 1:2006)

Diese Internationale Norm beschreibt ein Verfahren zur Bestimmung, ob zwischen den Proben von zwei Prüfmaterialien ein wahrnehmbarer sensorischer Unterschied oder eine Ähnlichkeit in Bezug auf die Intensität einer sensorischen Merkmalseigenschaft vorliegt. Diese Prüfung wird manchmal auch als gerichtete Prüfung auf Unterschied oder 2 AFC-Prüfung (en: Alternative Forced Choice, de: Zwangsauswahl zwischen Alternativen) bezeichnet. Tatsächlich ist die paarweise Vergleichsprüfung eine Zwangsauswahlprüfung (Forced-Choice-Prüfung) zwischen zwei Alternativen.
ANMERKUNG   Die paarweise Vergleichsprüfung ist die einfachste verfügbare Einstufungsprüfung, weil sie sich nur auf zwei Proben bezieht.
Das Verfahren ist unabhängig davon anwendbar, ob der Unterschied nur bei einer einzelnen sensorischen Merkmalseigenschaft oder bei mehreren Merkmalseigenschaften vorliegt; das bedeutet, es ermöglicht die Bestimmung, ob ein wahrnehmbarer Unterschied in Bezug auf eine vorgegebene Merkmalseigenschaft vorliegt, und die Festlegung der Richtung des Unterschieds, es gibt jedoch keinen Hinweis auf die Größe dieses Unterschieds. Das Fehlen eines Unterschieds hinsichtlich der untersuchten Merkmalseigenschaft bedeutet nicht, dass zwischen den beiden Prüfmaterialien kein Unterschied vorliegt.
Dieses Verfahren ist nur anwendbar, wenn die Prüfmaterialien relativ homogen sind.
Das Verfahren eignet sich besonders für
a)   die Untersuchung daraufhin
   ob ein wahrnehmbarer Unterschied vorliegt (paarweise Prüfung auf Unterschied) oder
   ob kein wahrnehmbarer Unterschied vorliegt (paarweise Prüfung auf Ähnlichkeit), wenn zum Beispiel Änderungen bei den Zutaten oder Arbeitsschritten von Verarbeitung, Verpackung, Handhabung oder Lagerung vorgenommen wurde, oder
b)   die Auswahl, Schulung und Leistungsüberprüfung von Prüfpersonen.

Analyse sensorielle - Méthodologie - Essai de comparaison par paires (ISO 5495:2005 et ISO 5495:2005/Cor 1:2006)

L'ISO 5495:2005 décrit un mode opératoire permettant de déterminer s'il existe une différence sensorielle perceptible ou une similitude entre les échantillons de deux produits sur l'intensité d'une propriété sensorielle. Cet essai est parfois également appelé essai de différence directionnel ou essai 2-AFC (Alternative Forced Choice). En effet l'essai de comparaison par paires est un essai à choix forcé entre deux alternatives.
La méthode est applicable s'il existe une différence pour une seule propriété sensorielle ou pour plusieurs, ce qui signifie qu'elle permet de déterminer s'il existe une différence perceptible sur une propriété donnée, de préciser le sens de la différence, mais elle ne donne pas d'indications sur l'amplitude de la différence. L'absence de différence pour l'attribut étudié ne signifie pas qu'il n'existe pas de différence entre les deux produits.
La présente méthode n'est applicable que si les produits sont relativement homogènes.
La méthode est efficace pour (1) déterminer s'il existe (essai par paires de différence), ou s'il n'existe pas de différence perceptible (essai par paires de similitude), quand, par exemple, des modifications sont apportées aux ingrédients, à la transformation, à l'emballage, aux opérations de manutention ou de stockage, ou (2) sélectionner, entraîner et contrôler les sujets.
Il est nécessaire de savoir avant la réalisation de l'essai si l'on se trouve dans un cas d'essai unilatéral (l'expérimentateur a un a priori sur le sens de la différence et l'hypothèse alternative correspond à l'existence d'une différence dans le sens attendu) ou dans un cas d'essai bilatéral (l'expérimentateur n'a pas d'a priori sur le sens de la différence et l'hypothèse alternative correspond à l'existence d'une différence dans un sens ou dans l'autre).
L'essai par paires peut également être utilisé pour comparer deux produits en terme de préférence.

Senzorična analiza - Metodologija - Preskus s primerjavo v parih (ISO 5495:2005 in ISO 5495:2005/Cor 1:2006)

Ta mednarodni standard opisuje postopek za ugotavljanje, ali obstaja zaznavna senzorična razlika oz. podobnost med vzorci dveh izdelkov v smislu intenzitete senzorične lastnosti. Ta preskus se včasih imenuje tudi preskus usmerjene razlike ali preskus 2-AFC (metoda prisilne izbire). Preskus s primerjavo v parih je pravzaprav preskus z uporabo metode prisilne izbire med dvema alternativama. Metoda se lahko uporablja, če obstaja razlika v eni ali več senzorskih lastnostih; to pomeni, da je mogoče ugotoviti, ali obstaja zaznavna razlika, ki zadeva podano lastnost, ter določiti smer razlike, pri čemer podatek o obsegu razlike ni na voljo. Odsotnost razlike za lastnost, ki se preučuje, ne pomeni, da med izdelkoma ne obstaja nobena razlika.

General Information

• Status: Published
• Publication Date: 30-Sep-2007
• ICS: 67.240 - Sensory analysis
• Technical Committee: KŽP - Agricultural food products
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 14-Sep-2007
• Due Date: 19-Nov-2007
• Completion Date: 01-Oct-2007
• Ref Project: EN ISO 5495:2007 - Sensory analysis - Methodology - Paired comparison test (ISO 5495:2005 and ISO 5495:2005/Cor 1:2006)

Relations

• Replaces: SIST ISO 5495:1997 - Sensory analysis -- Methodology -- Paired comparison test
• Effective Date: 01-Dec-2012
• Amended By: SIST EN ISO 5495:2007/A1:2016 - Sensory analysis - Methodology - Paired comparison test (ISO 5495:2005/Amd 1:2016)
• Effective Date: 01-May-2015

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN ISO 5495:2007
01-november-2007
6HQ]RULþQDDQDOL]D0HWRGRORJLMD3UHVNXVVSULPHUMDYRYSDULK,62LQ
,62&RU
Sensory analysis - Methodology - Paired comparison test (ISO 5495:2005 and ISO
5495:2005/Cor 1:2006)
Sensorische Analyse - Prüfverfahren - Paarweise Vergleichsprüfung (ISO 5495:2005
und ISO 5495:2005/Cor 1:2006)
Analyse sensorielle - Méthodologie - Essai de comparaison par paires (ISO 5495:2005 et
ISO 5495:2005/Cor 1:2006)
Ta slovenski standard je istoveten z: EN ISO 5495:2007
ICS:
67.240 6HQ]RULþQDDQDOL]D Sensory analysis
SIST EN ISO 5495:2007 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------

EUROPEAN STANDARD
EN ISO 5495
NORME EUROPÉENNE
EUROPÄISCHE NORM
July 2007
ICS 67.240

English Version
Sensory analysis - Methodology - Paired comparison test (ISO
5495:2005 and ISO 5495:2005/Cor 1:2006)
Analyse sensorielle - Méthodologie - Essai de comparaison Sensorische Analyse - Prüfverfahren - Paarweise
par paires (ISO 5495:2005 et ISO 5495:2005/Cor 1:2006) Vergleichsprüfung (ISO 5495:2005 und ISO 5495:2005/Cor
1:2006)
This European Standard was approved by CEN on 12 July 2007.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the CEN Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as the
official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2007 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 5495:2007: E
worldwide for CEN national Members.

---------------------- Page: 2 ----------------------

EN ISO 5495:2007 (E)






Foreword


The text of ISO 5495:2005 and ISO 5495:2005/Cor 1:2006 has been prepared by Technical
Committee ISO/TC 34 "Agricultural food products” of the International Organization for
Standardization (ISO) and has been taken over as EN ISO 5495:2007 by Technical Committee
CEN/SS C01 "Food Products", the secretariat of which is held by CMC.

This European Standard shall be given the status of a national standard, either by publication of
an identical text or by endorsement, at the latest by January 2008, and conflicting national
standards shall be withdrawn at the latest by January 2008.

According to the CEN/CENELEC Internal Regulations, the national standards organizations of
the following countries are bound to implement this European Standard: Austria, Belgium,
Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece,
Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United
Kingdom.


Endorsement notice

The text of ISO 5495:2005 and ISO 5495:2005/Cor 1:2006 has been approved by CEN as EN
ISO 5495:2007 without any modifications.

2

---------------------- Page: 3 ----------------------

INTERNATIONAL ISO
STANDARD 5495
Third edition
2005-11-15

Sensory analysis — Methodology —
Paired comparison test
Analyse sensorielle — Méthodologie — Essai de comparaison par
paires




Reference number
ISO 5495:2005(E)
©
ISO 2005

---------------------- Page: 4 ----------------------

ISO 5495:2005(E)
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.


©  ISO 2005
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail [e-mail]
Web www.iso.org
Published in Switzerland

ii © ISO 2005 – All rights reserved

---------------------- Page: 5 ----------------------

ISO 5495:2005(E)
Contents Page
Foreword. iv
1 Scope . 1
2 Normative references . 2
3 Terms and definitions. 3
4 Principle. 4
5 General test conditions. 4
6 Assessors. 5
6.1 Qualification . 5
6.2 Number of assessors . 5
7 Procedure . 5
8 Analysis and interpretation of results . 6
8.1 When testing for a difference . 6
8.2 When testing for similarity . 6
9 Report . 7
10 Precision and bias . 7
Annex A (normative) Tables. 8
Annex B (informative) Examples . 15
Bibliography . 21

© ISO 2005 – All rights reserved iii

---------------------- Page: 6 ----------------------

ISO 5495:2005(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 5495 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 12, Sensory
analysis.
This third edition cancels and replaces the second edition (ISO 5495:1983), which has been technically
revised.

iv © ISO 2005 – All rights reserved

---------------------- Page: 7 ----------------------

INTERNATIONAL STANDARD ISO 5495:2005(E)

Sensory analysis — Methodology — Paired comparison test
1 Scope
This International Standard describes a procedure for determining whether there exists a perceptible sensory
difference or a similarity between samples of two products concerning the intensity of a sensory attribute. This
test is sometimes also referred to as a directional difference test or a 2-AFC test (Alternative Forced Choice).
In fact, the paired comparison test is a forced choice test between two alternatives.
NOTE The paired comparison test is the simplest existing classification test since it concerns only two samples.
The method is applicable whether a difference exists in a single sensory attribute or in several, which means
that it enables determination of whether there exists a perceptible difference concerning a given attribute, and
the specification of the direction of difference, but it does not give any indication of the extent of that difference.
The absence of difference for the attribute under study does not signify that there does not exist any
difference between the two products.
This method is only applicable if the products are relatively homogeneous.
The method is effective
a) for determining
⎯ whether a perceptible difference exists (paired difference test), or
⎯ whether no perceptible difference exists (paired similarity test) when, for example, modifications are
made to ingredients, processing, packaging, handling or storage operations, or
b) for selecting, training and monitoring assessors.
It is necessary to know, prior to carrying out the test, whether the test is a one-sided test (the test supervisor
knows a priori the direction of the difference, and the alternative hypothesis corresponds to the existence of a
difference in the expected direction) or a two-sided test (the test supervisor does not have any a priori
knowledge concerning the direction of the difference, and the alternative hypothesis corresponds to the
existence of a difference in one direction or the other).
The paired test can also be used in order to compare two products in terms of preference. The different cases
of use of the paired test are summarized in Figure 1.
© ISO 2005 – All rights reserved 1

---------------------- Page: 8 ----------------------

ISO 5495:2005(E)

NOTE Only non-hedonic tests are dealt with in this International Standard.
Figure 1 — Possible different cases of use of the paired comparison test
EXAMPLE 1 (Case a) The production of a biscuit has been modified in order to render it more crisp. It is desired to
check whether this increase is perceptible. Therefore it is necessary to try to highlight a difference to see whether the new
product is perceived as being crispier than the usual product (control).
EXAMPLE 2 (Case b) A manufacturer knows that the product may contain traces of an ingredient which imparts an
off-flavour to the product. He therefore wishes to determine the maximum acceptable quantity so that the flavour
difference with a reference product without this ingredient is barely perceptible and therefore without any regrettable
consequences.
EXAMPLE 3 (Case c) It is desired to produce a new soup and to compare two ingredients which will provide the salty
flavour. For cost-intensive reasons, the ingredient which, at the same concentration, will provide the strongest salty flavour
is sought. Therefore it is necessary to try to highlight a difference. It is not known a priori which ingredient will produce the
strongest salty flavour.
EXAMPLE 4 (Case d) A manufacturer of plastics used, in particular, by car manufacturers for dashboards is seeking,
for economic reasons, to replace the usual lubricant by a new one, but does not wish that the new plastics formula be
perceived as presenting less or more surface slip than the usual one. It is a question of determining whether, for a same
concentration, the new lubricant provides the same “surface slip” level as the usual product. It is necessary to show that
both lubricants are similar in terms of “surface slip”, but it is not known a priori which lubricant can produce the highest
surface slip characteristics.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 5492 1992, Sensory analysis — Vocabulary
ISO 6658:1985, Sensory analysis — Methodology — General guidance
ISO 8586-1:1993, Sensory analysis — General guidance for the selection, training and monitoring of
assessors — Part 1: Selected assessors
ISO 8586-2:1994, Sensory analysis — General guidance for the selection, training and monitoring of
assessors — Part 2: Experts
ISO 8589:1988, Sensory analysis — General guidance for the design of test rooms
2 © ISO 2005 – All rights reserved

---------------------- Page: 9 ----------------------

ISO 5495:2005(E)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 5492 and the following apply.
3.1
α (alpha) risk
probability of concluding that a perceptible difference exists when one does not exist
NOTE This is also called a type I error, significance level or false-positive rate.
3.2
β (beta) risk
probability of concluding that no perceptible difference exists when one does exist
NOTE This is also called a type II error or false-negative rate.
3.3
difference
situation in which samples can be distinguished based on their sensory attributes
NOTE The proportion of assessments during which a perceptible difference is detected between the products for the
sensory attribute under study is given by the symbol p .
d
3.4
one-sided test
test in which the test supervisor has a priori knowledge concerning the direction of difference
NOTE The null hypothesis is H , the products are not different; the proportion of correct responses observed, p, is
0
equal to 1/2. The alternative hypothesis is H , p > 1/2.
1
3.5
two-sided test
test in which the test supervisor does not have any a priori knowledge concerning the direction of difference
NOTE The null hypothesis is H , the products are not different; the proportion of responses observed for one of the
0
samples, p, is equal to 1/2. The alternative hypothesis is H , p ≠ 1/2.
1
3.6
correct responses
expected responses
number of assessors, in the case of a one-sided test, having selected the sample expected by the test
supervisor to be the most intense for the sensory attribute under study
3.7
consensual responses
highest value, in the case of a one-sided test, of the number of assessors having selected sample A and those
having selected sample B
NOTE This is calculated as above since there are not any correct responses.
3.8
product
material to be evaluated
3.9
sample
unit of product prepared, presented and evaluated during the course of the test
© ISO 2005 – All rights reserved 3

---------------------- Page: 10 ----------------------

ISO 5495:2005(E)
3.10
sensitivity
general term employed to summarize the performance characteristics of the test
NOTE In statistical terms, the sensitivity of the test is defined by the values of α, β and p
.
d
3.11
similarity
situation in which any perceptible differences between the samples are so small that the products can be used
interchangeably
4 Principle
The number of assessors is chosen on the basis of the sensitivity desired for the test (See 6.2 and the
footnote that accompanies Tables A.4 and A.5).
The assessors receive a set of two samples (i.e. a pair). They designate the sample which they consider to be
the most intense regarding the sensory attribute under consideration, even if this choice is based only on a
guess.
NOTE One of the samples may be a control.
The number of times that each sample is selected is counted and the significance is determined by reference
to a statistical table, taking into consideration the results obtained for the expected sample (one-sided test) or
the highest number of responses obtained for either of the samples (two-sided test).
5 General test conditions
5.1 Define the objective of the test in a clear way to determine if the attempt is to be a one-sided or a two-
sided test, if it is a difference or similarity test, and which is the most appropriate sensitivity.
5.2 Carry out the test under conditions that prevent all communication among assessors until the
evaluations have been completed, using facilities and booths complying with ISO 8589.
5.3 Prepare the samples out of sight of the assessors and in an identical manner for each one of them; i.e.
same apparatus, same vessels.
5.4 Assessors shall not be able to draw any conclusions regarding the intensity of the attribute from the
manner in which the samples are presented to them. For example, for a tactile test, any differences in
appearance shall be avoided. Mask all colour differences if the test objective does not concern the colour by
using light filters and/or subdued lighting. The samples may also be presented successively and non-
simultaneously in the case of slight differences in appearance.
5.5 Code the samples or the vessels containing the samples in a uniform manner, preferably using 3-digit
numbers chosen at random for each test. Each pair is composed of two samples, each with a different code.
Preferably, different codes should be used for each assessor during a session. However, the two same codes
may be used for all assessors within a test, provided that each code is used only once per assessor during a
test session (e.g. if several paired tests on different products are being conducted during the same session).
5.6 The quantity or volume served shall be identical for the two samples constituting each pair, just as that
of all the other samples in a series of tests on a given type of product. The quantity or volume to be assessed
can be imposed. If it is not, it should however be specified to the assessors to take quantities or volumes that
are always similar whatever the sample.
5.7 The temperature of the samples constituting each pair shall be identical just as that of all the other
samples in a series of tests on a given type of product. It is preferable to present the samples at the
temperature at which the product is generally consumed.
4 © ISO 2005 – All rights reserved

---------------------- Page: 11 ----------------------

ISO 5495:2005(E)
5.8 The assessors shall be told whether or not they have to follow a special protocol in order to assess the
products (e.g. whether or not to swallow the samples for a taste test, or carry out a specific gesture for a
tactile test) or whether they are free to do as they please. In this latter case, they should be requested to
proceed in the same manner for all the samples.
5.9 During the test sessions, avoid giving information about product identity, expected treatment effects or
individual performance until all tests are completed.
6 Assessors
6.1 Qualification
All assessors should possess the same level of qualification, this level being chosen on the basis of the test
objective (see ISO 8586-1 and ISO 8586-2). Experience and familiarity with the product can increase the
performance of an assessor and can consequently increase the likelihood of finding a significant difference.
Monitoring the performance of assessors over time may prove to be useful for increased sensitivity.
All assessors shall be familiar with the mechanisms of the paired test (the scoresheet, the task and the
evaluation procedure). In addition, assessors shall be capable of recognising the sensory attribute on which
the test is based. This attribute shall be defined verbally, by means of a reference substance or by presenting
a few samples having different levels of intensity for the attribute under examination.
6.2 Number of assessors
Choose the number of assessors so as to obtain the level of sensitivity required for the test (see Table A.4 for
a one-sided test and Table A.5 for a two-sided test). The use of a large number of assessors increases the
likelihood of detecting small differences between the products. However, in practice, the number of assessors
is often determined by material conditions (e.g. duration of the experiment, number of available assessors,
quantity of product). When conducting a difference test, the number of assessors is typically approximately
24 to 30. When conducting a similarity test, about twice as many assessors (i.e. approximately 60) are
required for equivalent sensitivity. When testing for similarity, evaluations should not be replicated by the
same assessors. For a difference test, replications may be considered but should still be avoided whenever
possible. However, if replicate evaluations are required in order to produce a sufficient total number of
evaluations, every effort should be made to have each assessor perform the same number of replicate
evaluations. For example, if only 10 assessors are available, have each assessor perform three paired tests in
order to obtain a total of 30 evaluations.
NOTE Analysing three evaluations performed by 10 assessors as 30 independent evaluations is not valid when
testing for similarity using Table A.3. However, the difference test using Tables A.1 and A.2 is valid even when replicate
[5], [6] [1], [2]
evaluations are performed . Some recent publications on replicated discrimination tests suggest alternative
approaches for analysing replicated evaluations.
7 Procedure
7.1 Prepare the worksheets and scoresheets (see Figures B.1, B.2 and B.3) prior to conducting the test so
as to use an equal number of the two possible presentation sequences of both products, A and B.
7.2 Present the two samples constituting a pair successively or simultaneously (see 5.4). In the case of
simultaneous presentation, arrange the two samples in the same manner for each assessor (in line from left to
right, in line from the bottom up, etc.). The assessors shall examine the two samples constituting the pair in
the order indicated in the scoresheet, but assessors are generally authorized to make repeated evaluations of
each sample if so wished (if, of course, the nature of the product allows for repeated evaluations).
7.3 Provision should be made for one scoresheet per pair of samples. If an assessor is to perform more
than one test during the course of a session, collect the completed scoresheet and the unused samples prior
© ISO 2005 – All rights reserved 5

---------------------- Page: 12 ----------------------

ISO 5495:2005(E)
to serving the subsequent pair. The assessor can neither go back to any of the previous samples, nor modify
his/her verdict concerning any of the previous tests.
7.4 Do not ask any questions about preference, acceptance or degree of difference following the selection
of the most intense sample. The selection the assessor has just made may bias the response to any
additional questions. Responses to such questions may be obtained through separate tests concerning
preference, acceptance, degree of difference, etc. (see ISO 6658). A “Comments” section requesting the
reasons for the choice may be included for the assessors' remarks.
7.5 The paired test is a “forced choice” procedure; assessors are not allowed to choose the “no difference”
option. An assessor who detects no difference between the samples should be instructed to select one of the
samples and to indicate that the selection was only a guess in the “Comments” section of the scoresheet.
8 Analysis and interpretation of results
8.1 When testing for a difference
8.1.1 Case of a one-sided test
Use Table A.1 to analyse the data obtained from a paired test. If the number of correct responses is greater
than or equal to the number given in Table A.1 (corresponding to the number of assessors and to the α-risk
level chosen for the test), conclude that a perceptible difference exists between the samples (see B.1).
If desired, calculate a confidence interval on the proportion of the population able to distinguish the samples.
This method is described in B.5.
No conclusion should be drawn for maximum numbers of correct responses under n/2.
8.1.2 Case of a two-sided test
Use Table A.2 to analyse the data obtained from a paired test. If the number of consensual responses is
greater than or equal to the number given in Table A.2 (corresponding to the number of assessors and to the
α-risk level chosen for the test), conclude that a perceptible difference exists between the samples (see B.3).
If desired, calculate a confidence interval on the proportion of the population able to distinguish the samples.
This method is described in B.5.
1)
8.2 When testing for similarity
8.2.1 Case of a one-sided test
Use Table A.3 to analyse the data obtained from a paired test. If the number of correct responses is less than
or equal to the number given in Table A.3 (corresponding to the number of assessors, to the β-risk level and
to the value of p chosen for the test), conclude that no meaningful difference exists between the samples
d
(see B.2). If the results are to be compared from one test to another, then the same value of p should be
d
chosen for all tests.
If desired, calculate a confidence interval on the proportion of the population able to distinguish the samples.
This method is described in B.5.
No conclusion should be drawn for maximum numbers of correct responses under n/2.

1)
In this International Standard, “similar” does not mean “identical”. This term signifies rather that the two products are
sufficiently alike to be used interchangeably. It is impossible to prove that two products are identical. However, it can be

demonstrated that any difference that does exist between two products is so minor as to have no practical significance.
6 © ISO 2005 – All rights reserved

---------------------- Page: 13 ----------------------

ISO 5495:2005(E)
8.2.2 Case of a two-sided test
Use Table A.3 to analyse the data obtained from a paired test. If the number of consensual responses is less
than or equal to the number given in Table A.3 (corresponding to the number of assessors, to the β-risk level
and to the value of p chosen for the test), conclude that no meaningful difference exists between the samples
d
(see B.4). If the results are to be compared from one test to another, then the same value of p should be
d
chosen for all tests.
If desired, calculate a confidence interval on the proportion of the population able to distinguish the samples.
This method is described in B.5.
9 Report
Report the test objective, the results and the conclusions. It is recommended to add the following additional
information:
⎯ the purpose of the test and the nature of the treatment being studied;
⎯ the complete identification of the samples: origin, method of preparation, quantity, shape, storage prior to
testing, quantity served, temperature (the information concerning the sample should indicate that all
storage, handling and preparation operations have been carried out so as to yield samples that differ only
due to the variable of interest, if any);
⎯ the number of assessors, the number of correct or consensual responses and the result of the statistical
evaluation (including the values of α, β and p used for the test);
d
⎯ the a
...