Comparative Sensitivity of Pair and Triad Flavor Intensity Difference Tests

Alternative simple experimental designs for sensory difference tests of flavor intensity lead to the procedures termed pair, duo-trio and triangular tests (3). In the first, a unit trial consists in submitting coded aliquots of the two batches in question to a subject in the sequence (X), (Y) or (Y), (X) and requiring him to rank them in the order of appraised flavor strength. In the second, it consists in submitting identified X or Y with the coded sequence (X), (Y) or (Y), (X) and requiring the subject to attempt to match the identified with the like coded aliquot. In the third, it consists in submitting one of the completely coded sequences (X), (X), (Y); (X), (Y), (X); (Y), (X), (X); (Y), (Y), (X); (Y), (X), (Y) or (X), (Y), (Y) and again requiring an attempted matching of like aliquots. Inferences respecting the occurrence or non-occurrence of real discrimination are then made by relating the actual frequency of ranking or matching in repeated trials to percentage points of the binomial distribution expected in the absence of discrimination. It has been suggested (4) that the triangular test is obviously the most efficient but experimental evidence to the contrary has been reported (1). This note indicates some statistical considerations relevant to efficiency comparisons, and applies them to additional data.