ISO 16820:2004 describes 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 a perceptible difference results, or a perceptible difference does not result when, for example, a change is made in ingredients, processing, packaging, handling or storage; or b) for selecting, training and monitoring assessors.