  In this contribution we describe a novel procedure to represent fuzziness in
rating scales in terms of fuzzy numbers. Following the rationale of fuzzy
conversion scale, we adopted a two-step procedure based on a psychometric model
(i.e., Item Response Theory-based tree) to represent the process of answer
survey questions. This provides a coherent context where fuzzy numbers, and the
related fuzziness, can be interpreted in terms of decision uncertainty that
usually affects the rater's response process. We reported results from a
simulation study and an empirical application to highlight the characteristics
and properties of the proposed approach.
