title: Application of the Rasch rating scale model to the assessment of quality of life of persons with intellectual disability.
abstract: BACKGROUND
  Most instruments that assess quality of life have been validated by means of the classical test theory (CTT). However, CTT limitations have resulted in the development of alternative models, such as the Rasch rating scale model (RSM). The main goal of this paper is testing and improving the psychometric properties of the INTEGRAL Quality of Life Scale (i.e., fit statistics, person and item reliability coefficients) with RSM.
  
  
  METHODS
  The sample comprised 271 Spanish adults with intellectual disability.
  
  
  RESULTS
  The results showed that the data fitted the model, point-biserial correlations were adequate, items showed precision, reliability of items (.98) and persons (.89) were adequate, and the response categories were suitable (thresholds were ordered). However, one item ("I feel excluded from society") did not fit the model and a few items were too easy for participants to achieve.
  
  
  CONCLUSIONS
  Although it seems necessary to include more difficult items and to delete one, the INTEGRAL Scale is a useful instrument with evidence of validity.
authors.affiliation: University of Oviedo, Oviedo, Spain. gomezlaura@uniovi.es
authors.forename: Laura E
authors.initials: LE
authors.lastname: Gómez
authors.forename: Benito
authors.initials: B
authors.lastname: Arias
authors.forename: Miguel Ángel
authors.initials: MÁ
authors.lastname: Verdugo
authors.forename: Patricia
authors.initials: P
authors.lastname: Navas
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008607:Intellectual Disability / Q000523:psychology*; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D011594:Psychometrics / Q000379:methods*; D011788:Quality of Life / Q000523:psychology*; D015203:Reproducibility of Results; D013030:Spain; D011795:Surveys and Questionnaires / Q000592:standards*; D055815:Young Adult