Use of Purchase Preference Options to Increase “No Preference” Frequencies in Placebo Preference Tests

Besides responses to the different stimuli being tested in a paired preference test, responses to identical “placebo” stimuli can be used as a screening tool to identify biased consumers. Those consumers who give preference responses to identical stimuli can be assumed to be biased. Accordingly, only the data from unbiased consumers need to be considered for the different stimuli. The problem with this procedure is that the sample size is reduced. The goal of the present research was to see whether using options associated with purchase intent, elicited a greater number of “No Preference” responses to identical “placebo” stimuli. It was found that they did. The increase was large when the preference options implied exclusivity. In conditions where the preference strength options were not so strong, the frequency of “No Preference” responses dropped accordingly. PRACTICAL APPLICATIONS A problem with paired preference testing is the tendency of consumers to give false preferences, which produces the seriously misleading overestimation of the proportion of consumers who have preferences for one or other of the products being assessed. The “placebo” condition is an important control for alleviating this problem. The statistical analysis can be improved by finding a protocol that maximizes the proportion of “No Preference” responses in the placebo condition. The key finding here is that using purchase intent questions rather than preference questions may possibly provide a way of achieving this aim.