title: Computerized adaptive testing of population psychological distress: simulation-based evaluation of GHQ-30.
abstract: Goldberg's General Health Questionnaire (GHQ) items are frequently used to assess psychological distress but no study to date has investigated the GHQ-30's potential for adaptive administration. In computerized adaptive testing (CAT) items are matched optimally to the targeted distress level of respondents instead of relying on fixed-length versions of instruments. We therefore calibrate GHQ-30 items and report a simulation study exploring the potential of this instrument for adaptive administration in a longitudinal setting.
  
  
  
  GHQ-30 responses of 3445 participants with 2 completed assessments (baseline, 7-year follow-up) in the UK Health and Lifestyle Survey were calibrated using item response theory. Our simulation study evaluated the efficiency of CAT administration of the items, cross-sectionally and longitudinally, with different estimators, item selection methods, and measurement precision criteria.
  
  
  
  To yield accurate distress measurements (marginal reliability at least 0.90) nearly all GHQ-30 items need to be administered to most survey respondents in general population samples. When lower accuracy is permissible (marginal reliability of 0.80), adaptive administration saves approximately 2/3 of the items. For longitudinal applications, change scores based on the complete set of GHQ-30 items correlate highly with change scores from adaptive administrations.
  
  
  
  The rationale for CAT-GHQ-30 is only supported when the required marginal reliability is lower than 0.9, which is most likely to be the case in cross-sectional and longitudinal studies assessing mean changes in populations. Precise measurement of psychological distress at the individual level can be achieved, but requires the deployment of all 30 items.
authors.affiliation: Department of Health Sciences, University of York, Area 4, ARRC Building, York, YO10 5DD, UK. js883@cam.ac.uk.|Department of Psychiatry, University of Cambridge, Herchel Smith Bldg, Robinson Way, Cambridge, CB2 0SZ, UK. js883@cam.ac.uk.
authors.forename: Jan
authors.identifier: 0000-0002-9693-9930
authors.initials: J
authors.lastname: Stochl
authors.affiliation: Department of Health Sciences, University of York, Area 4, ARRC Building, York, YO10 5DD, UK.|Hull York Medical School (HYMS), University of York, Area 4, ARRC Building, York, YO10 5DD, UK.
authors.forename: Jan R
authors.initials: JR
authors.lastname: Böhnke
authors.affiliation: Department of Health Sciences, University of York, Area 4, ARRC Building, York, YO10 5DD, UK.
authors.forename: Kate E
authors.initials: KE
authors.lastname: Pickett
authors.affiliation: Department of Health Sciences, University of York, Area 4, ARRC Building, York, YO10 5DD, UK.|Hull York Medical School (HYMS), University of York, Area 4, ARRC Building, York, YO10 5DD, UK.|School of Nursing and Health Sciences, University of Dundee, 11 Airlie Place, Dundee, DD1 4HJ, UK.
authors.forename: Tim J
authors.initials: TJ
authors.lastname: Croudace
mesh_terms: D000328:Adult; D003198:Computer Simulation; D003430:Cross-Sectional Studies; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D006801:Humans; D008137:Longitudinal Studies; D011569:Psychiatric Status Rating Scales / Q000592:standards*; D011594:Psychometrics / Q000379:methods*; D015203:Reproducibility of Results; D013315:Stress, Psychological / Q000175:diagnosis*
keywords: Bifactor model; Computerized adaptive testing; General Health Questionnaire; Item response theory; Measurement invariance