Talk: A Thurstonian Comparison of the Tetrad and Degree of Difference Tests

Presented at the 2014 Sensometrics Conference in Chicago, Illinois.

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 (DOD) test. In this presentation, we share the results of such a comparison by considering, from a theoretical perspective, the differences between both power and precision for the Tetrad and DOD tests. In particular we show that, theoretically and for the range of sensory effect sizes likely to be of interest in consumer research, the Tetrad test is more powerful and more precise than the DOD test. Even so, if there is substantially more perceptual noise in the Tetrad test from the two additional stimuli on a single trial, it is possible that performance of the DOD could surpass the performance of the Tetrad test in practice. To quantify this last statement, we quantify the additional noise required to negate the theoretical advantage of the Tetrad test before concluding with guidelines for practitioners as to when to use which test.

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A Thurstonian Comparison of the Tetrad and Degree of Difference Tests

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