Item Response Theory as applied to psychiatry

• Grant number: 06/06089-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: January 01, 2007
• End date: December 31, 2007
• Field of knowledge: Physical Sciences and Mathematics - Probability and Statistics - Statistics
• Principal Investigator: Mariana Cúri
• Grantee: Daniela de Jesus Peron
• Host Institution: Instituto de Ciências Matemáticas e de Computação (ICMC). Universidade de São Paulo (USP). São Carlos , SP, Brazil

Abstract

In psychiatric scientific research subjective characteristics of the individual such as depression, anxiety and phobias are often evaluated. Data are collected through questionnaires with items in an attempt to identify the presence and intensity of certain symptoms associated to some psychiatric disease. The psychometric properties of the questionnaire are assessed to determine its quality and usefulness. Recently, the use of Item Response Theory (IRT) with this intention has been spread out. The aim of this research is studying two models of IRT, the two-parameter logistic model and the Samejima’s model, in order to assess the questionnaire quality. Both models are interpreted, considering the psychiatric viewpoint, and applied to real data collected to evaluate depression. In addition, the parameter estimation methods are described in detail. (AU)