title: Item response theory for measurement validity.
abstract: Item response theory (IRT) is an important method of assessing the validity of measurement scales that is underutilized in the field of psychiatry. IRT describes the relationship between a latent trait (e.g., the construct that the scale proposes to assess), the properties of the items in the scale, and respondents' answers to the individual items. This paper introduces the basic premise, assumptions, and methods of IRT. To help explain these concepts we generate a hypothetical scale using three items from a modified, binary (yes/no) response version of the Center for Epidemiological Studies-Depression scale that was administered to 19,399 respondents. We first conducted a factor analysis to confirm the unidimensionality of the three items and then proceeded with Mplus software to construct the 2-Parameter Logic (2-PL) IRT model of the data, a method which allows for estimates of both item discrimination and item difficulty. The utility of this information both for clinical purposes and for scale construction purposes is discussed.
authors.affiliation: Department of Biostatistics and Epidemiology, Georgia Regents University, Medical College of Georgia, Augusta, GA, United States.
authors.forename: Frances M
authors.initials: FM
authors.lastname: Yang
authors.affiliation: Department of Oral Maxillofacial Surgery, College of Dental Medicine, Medical College of Georgia, Augusta, GA, United States.
authors.forename: Solon T
authors.initials: ST
authors.lastname: Kao
keywords: CES-D; Health and Retirement Study; Item Response Theory; Mplus; latent variable modeling
references.citation: J Pers Soc Psychol. 2000 Feb;78(2):350-65
references.pmid: 10707340
references.citation: Psychosom Med. 2008 Nov;70(9):993-1004
references.pmid: 18981269
references.citation: Psychol Assess. 2011 Jun;23(2):558-62
references.pmid: 21319906
references.citation: Psychol Bull. 1990 Mar;107(2):238-46
references.pmid: 2320703