The purpose of this research is to improve measurement of psychopathology through the use of item response theory (IRT). IRT is a set of statistical models and techniques used to evaluate items and score questionnaires, interviews, rating scales, etc. IRT techniques are preferable to classical test theory methods (e.g., Cronbach's alpha, summed scores), because IRT models provide detailed information about items that: a) aids in the creation of short, but reliable instruments, b) produces indices of scale precision that vary for different people to better reflect individual differences, and c) allows for the computation of scores that account for heterogeneity of discrimination ability among the items. However, currently implemented IRT models often assume that the construct measured by the items is normally distributed in the population, which is untenable for psychopathology. IRT analyses based on a false assumption about the distribution of the latent construct likely produce misleading results.
The first aim of the proposed study is to adapt existing IRT so that the distribution of a latent construct in the population is allowed to adopt nearly any shape. The new procedure and software will be tested with a computer simulation study, wherein the algorithm is applied to computer-generated data.
The second aim of the proposed study is to apply the new technique to data from two self-report questionnaires on obsessive-compulsive disorder symptoms, thereby producing distributions of the latent constructs and properties of the items, which may suggest potential revisions to the measures.

Agency
National Institute of Health (NIH)
Institute
National Institute of Mental Health (NIMH)
Type
Predoctoral Individual National Research Service Award (F31)
Project #
1F31MH067334-01
Application #
6584511
Study Section
Special Emphasis Panel (ZRG1-BBBP-5 (01))
Program Officer
Altman, Fred
Project Start
2002-09-12
Project End
2004-08-31
Budget Start
2002-09-12
Budget End
2003-09-11
Support Year
1
Fiscal Year
2002
Total Cost
$24,798
Indirect Cost
Name
University of North Carolina Chapel Hill
Department
Psychology
Type
Schools of Arts and Sciences
DUNS #
078861598
City
Chapel Hill
State
NC
Country
United States
Zip Code
27599
Tolin, David F; Woods, Carol M; Abramowitz, Jonathan S (2006) Disgust sensitivity and obsessive-compulsive symptoms in a non-clinical sample. J Behav Ther Exp Psychiatry 37:30-40
Rodebaugh, Thomas L; Woods, Carol M; Thissen, David M et al. (2004) More information from fewer questions: the factor structure and item properties of the original and brief fear of negative evaluation scale. Psychol Assess 16:169-81
Abramowitz, Jonathan S; Deacon, Brett J; Woods, Carol M et al. (2004) Association between Protestant religiosity and obsessive-compulsive symptoms and cognitions. Depress Anxiety 20:70-6
Deacon, Brett J; Abramowitz, Jonathan S; Woods, Carol M et al. (2003) The Anxiety Sensitivity Index - Revised: psychometric properties and factor structure in two nonclinical samples. Behav Res Ther 41:1427-49