A Comparison of Verbal and Numerical Judgments in the Analytic Hierarchy Process

In the Analytic Hierarchy Process (AHP), decision makers make pairwise comparisons of alternatives and criteria. The AHP allows to make these pairwise comparisons verbally or numerically. Although verbal statements are intuitively attractive for preference elicitation, there is overwhelming evidence that people have very different numerical interpretations of the same verbal expressions. This study explores the consequences of these differences for the quality of the AHP analysis. The results of the laboratory study with 180 participants confirm that the 1-to-9 conversion table, as is often used in the AHP, tends to overestimate differences in preference. Concerning the outcome of the AHP analysis the numerical mode shows slightly better results (not significant). Given the preference of many people for the verbal mode we conclude that if accuracy is not of the highest importance, the ease and comfort of verbal expressions may be worth the small loss in decision quality.