Presented at the 2013 Pangborn Symposium in Rio de Janeiro, Brazil.
The recurring need to assess product reformulations has kept difference testing at the forefront of sensory science. Within the realm of difference testing, the Tetrad test has risen in popularity recently as its superiority over the Triangle test has been demonstrated both in theory and in practice. But it remains to compare the Tetrad test in detail with other commonly used testing methods such as the Degree of Difference test (DOD). In this presentation, we provide such a comparison by considering, from a theoretical perspective, the differences between both power and precision of measurement for the Tetrad and DOD tests. In particular, we show that under ideal circumstances the performance of the DOD can approach that of the Tetrad test. But if the panelists are not trained to use the scale consistently, differences between panelists can comprise an important additional source of noise – this noise can undermine the DOD to the point that it performs as poorly as the Triangle test. Thus this presentation provides important information regarding the appropriate use of two commonly used difference testing methods.
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Power and Precision of the Tetrad and Degree of Difference Tests
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