title: Assessing the factor structure of a role functioning item bank.
abstract: OBJECTIVE
  Role functioning (RF) is an important part of health-related quality of life, but is hard to measure due to the wide definition of roles and fluctuations in role participation. This study aims to explore the dimensionality of a newly developed item bank assessing the impact of health on RF.
  
  
  METHODS
  A battery of measures with skip patterns including the new RF bank was completed by 2,500 participants answering only questions on social roles relevant to them. Confirmatory factor analyses were conducted for the participants answering items from all conceptual domains (N = 1193). Conceptually based dimensionality and method effects reflecting positively and negatively worded items were explored in a series of models.
  
  
  RESULTS
  A bi-factor model (CFI = .93, RMSEA = .08) with one general and four conceptual factors (social, family, occupation, generic) was retained. Positively worded items were excluded from the final solution due to misfit. While a single factor model with methods factors had a poor fit (CFI = .88, RMSEA = .13), high loadings on the general factor in the bi-factor model suggest that the RF bank is sufficiently unidimensional for IRT analysis.
  
  
  CONCLUSIONS
  The bank demonstrated sufficient unidimensionality for IRT-based calibration of all the items on a common metric and development of a computerized adaptive test.
authors.affiliation: Department of Quantitative Health Sciences, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, MA 01665-002, USA. Milena.Anatchkova@umassmed.edu
authors.forename: Milena D
authors.initials: MD
authors.lastname: Anatchkova
authors.forename: John E
authors.initials: JE
authors.lastname: Ware
authors.forename: Jakob B
authors.initials: JB
authors.lastname: Bjorner
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016009:Chi-Square Distribution; D003194:Computer-Assisted Instruction; D005163:Factor Analysis, Statistical; D005260:Female; D006306:Health Surveys; D006801:Humans; D008297:Male; D008875:Middle Aged; D008960:Models, Psychological; D015233:Models, Statistical; D011594:Psychometrics; D011788:Quality of Life / Q000523:psychology*; D012381:Role Playing; D012649:Self Concept; D013223:Statistics as Topic; D055815:Young Adult