ISO 16820:2019 pdf download

ISO 16820:2019 pdf download.Sensory analysis — Methodology — Sequential analysis
1 Scope
This document specifies a procedure for statistically analysing data from forced-choice sensory discrimination tests, such as the triangle, duo-trio, 3-AFC, 2-AFC, in which after every trial of the discrimination test the decision can be made to stop testing and declare a difference, to stop testing and declare no difference, or to continue testing. The sequential method often allows for a decision to be made after fewer trials of the discrimination test than would be required by conventional approaches that use predetermined numbers of assessments. The method is effective for: a) determining that either: 1) a perceptible difference results; or 2) a perceptible difference does not result when, for example, a change is made in ingredients, processing, packaging, handling or storage; b) selecting, training and monitoring assessors.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements 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, Sensory analysis — Vocabulary
3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 5492 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
4 Principle
The type of discrimination test (triangle, duo-trio, etc.) is chosen. The sensitivity of the test is defined by selecting values for α, β and p d .
The boundaries of the decision regions are computed based on α, β, p 0 and p 1 . After every trial of the discrimination test, the total number of correct responses [for the panel, see Clause 1 a), or per assessor,see Clause 1 b)] is compared to the decision boundaries to determine:
— if testing can be stopped and a difference can be declared;
— if testing can be stopped and no difference can be declared;
— if testing should continue.
5 Procedure
5.1 Construct a graph, as in Figure A.1, which illustrates the boundaries of the decision regions based on α, β, p 0 and p 1 , as follows. a) α and β are chosen based on the risks the researcher is willing to take of obtaining a false positive or a false-negative result, respectively. α is the probability of declaring that a difference exists when the true probability of a correct response is p 0 . β is the probability of failing to declare that a difference exists when the true probability of a correct response is p 1 (p 1 > p 0 ).