Psychological Treatment Inventory (PTI). Applying the Mixed rasch Model to Attachment Styles Scale (ASS)

This study describes a new instrument for evaluating interventions and outcomes using repeated measurements. The PTI (psychological treatment inventory) includes interacting biological, psychological, behavioural, social and environmental factors across various domains central to planning psychological treatment and evaluating its outcome. This study aims to explain the theoretical principles underlying the PTI and verify the dimensionality of the PTI ASS (attachment styles scale). Data from 1,800 individuals were analyzed by the means of WIN-MIRA (Windows-Mixed Item Response Analysis). Item parameters and Person Parameters were analyzed and discussed. Results confirmed that the PTI-ASS has good psychometrics properties and can be adopted for measuring attachment for both research and practice.