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Reducing Costs with Tetrad Testing

Ennis, J. M. and Rousseau, B. (2012). IFPress, 15(1) 4-5.



The Triangle test is one of the most popular discrimination methodologies used in consumer products companies. Beginning in 1941, Joseph E. Seagram and Sons were the first to employ it – since then it has been used in a variety of applications including product discrimination testing and panelist selection. An advantage of the Triangle test is that it does not require specification of the nature of the difference. Yet the Triangle test requires large sample sizes to be effective and, recently, the Tetrad test has received interest due to its potential to provide increased power without specification of an attribute. This greater power means that for the same sample size, an existing difference is less likely to be missed. Alternatively, greater power means that smaller sample sizes can be used to achieve the same performance as the Triangle - the sample sizes required by the Tetrad test are theoretically only one third that required by the Triangle test. Importantly, like the Triangle test, the Tetrad test does not require specification of a sensory attribute. The purpose of this technical report is to illustrate how sensory scientists can determine whether or not Tetrad testing is worth considering as a standard testing methodology within their discrimination testing programs.


Figure 2. Psychometric functions of Tetrad and Triangle tests. Proportion correct is a function of effect size (δ).

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