title: Understanding Rasch and item response theory models: applications to the estimation and validation of interval latent trait measures from responses to rating scale questionnaires.
abstract: BACKGROUND
  Modern psychometric theory is now routinely used in clinical vision research, as well as other areas of health research, to measure latent health states on continuous interval scales from responses to self-report rating scale questionnaires. Two competing theories are commonly employed: Rasch theory and item response theory.
  
  
  METHODS
  Because the field is currently in transition from using traditional scoring algorithms based on classical test theory to using the more modern approaches, this article offers a tutorial review of Rasch theory and item response theory and of the analytical methods employed by the two theories to estimate and validate measures.
authors.affiliation: Lions Vision Research and Rehabilitation Center, Wilmer Eye Institute, Johns Hopkins University School of Medicine, MD, USA. rmassof@lions.med.jhu.edu
authors.forename: Robert W
authors.initials: RW
authors.lastname: Massof
mesh_terms: D000203:Activities of Daily Living; D006302:Health Services Research; D006801:Humans; D015233:Models, Statistical; D011594:Psychometrics / Q000295:instrumentation* / Q000379:methods; D011788:Quality of Life; D015203:Reproducibility of Results; D018434:Sickness Impact Profile; D011795:Surveys and Questionnaires; D054928:Validation Studies as Topic; D014792:Visual Acuity / Q000502:physiology*