The Allen Diagnostic Module 2nd Ed. (ADM 2^nd Ed.) is a set of 27 craft-based assessment tasks based on the construct of functional cognition as it is described in the cognitive disabilities model. This theoretical model articulates hierarchies of cognitive abilities for individuals and cognitive difficulties for activity demands. The purpose of this study was to contribute to the validity argument supporting the theory-based inferences that occupational therapists make based on ADM 2^nd Ed. scores. More specifically this study was designed to gather empirical evidence related to the internal structure of the assessment, to the response processes of the therapists who administer these assessments, and to the individuals who complete the assessment tasks.

This study included two of the ADM 2^nd Ed. assessment tasks. Eight therapists administered these assessments, and 161 individuals completed these assessment tasks. The therapists used their routine clinical practices to determine holistic scores based on sets of rating criteria, completed a data collection form upon which they recorded individuals' responses to specific rating criteria, and commented on issues that may have affected each individual's performance during the assessment. They also watched and rated a set of video-taped administrations of these assessments.

The investigator analyzed the resulting data using many-faceted Rasch measurement models. The findings provided support for many of the inferences that therapists make based on ADM 2^nd Ed. scores. The Rasch-based analyses also allowed the investigator to describe response patterns related to specific subgroups of individuals (e.g., individuals who were not fluent in English) that did not match the expectations of the theoretical model. Therapists' notes suggested that they were often aware of these theoretically unexpected response patterns. The investigator identified the need for therapists who use this model to develop a clear, shared vocabulary to describe these situations. The investigator also provided an outline for building on this work to further develop the validity argument supporting inferences that therapists make based on ADM 2^nd Ed. scores.