Replicated difference and preference tests: how to account for inter-trialvariation

Binomial tests are often used in sensory difference and preference testing. Two assumptions underlie this use: (1) responses are independent and (2) c hoice probabilities do not vary from trial to trial. In many applications, the latter assumption is violated. In this paper we account for variation i n inter-trial choice probabilities using the beta distribution. The result of combining the binomial with the beta distribution is a compound distribu tion known as the beta-binomial. We show how to use the beta-binomial model for replicated difference and preference tests such as those used to suppo rt product claims. (C) 2000 Elsevier Science Ltd. All rights reserved.