Schematically, these tests may be described as follows; A & B are used for knowns, X and Y are used for different unknowns, while (AB) means that the order of presentation is unknown:
Paired comparison
XY or (AB) – two unknown samples, known to be different, test is which satisfies some criterion (X or Y); unlike the others this is not an equality test.
Duo-trio
AXY – one known, two unknown, test is which unknown is the known (X = A or Y = A)
Triangle
(XXY) – three unknowns, test is which is odd one out (Y = 1, Y = 2, or Y = 3).
ABX
ABX – two knowns, one unknown, test is which of the knowns the unknown is (X = A or X = B).
Duo-trio in constant reference mode
(AB)X – three unknowns, where it is stated that the first two are different, but which is which is not identified, test is which of the first two the third is (X = 1 or X = 2).
Tetrad
(XXYY) - four unknowns, test is to create groups of size two based on similarity (XX = (1,2), XX = (1,3) or XX = (1,4))[2]. Like the triangle test, this technique has a 1/3 probability that a random guess is correct. However, the tetrad test in some cases requires only one third the number of overall participants to establish statistical significance compared to the triangle test[3].
Signal Detection Theory
Notes and references
↑Rogers, Lauren; Hort, Joanne; Kemp, Sarah E.; Hollowood, Tracey, eds. (August 7, 2024). Discrimination Testing in Sensory Evaluation. John Wiley & Sons. doi:10.1002/9781118635353. ISBN9780470671405. Retrieved February 1, 2025.
↑Ennis, John M.; Jesionka, Virginie (2011-10-05). "THE POWER OF SENSORY DISCRIMINATION METHODS REVISITED". Journal of Sensory Studies. 26 (5): 371–382. doi:10.1111/j.1745-459X.2011.00353.x. ISSN0887-8250.