title: Examining differential responses of youth with and without autism on a measure of everyday activity performance.
abstract: OBJECTIVE
  This study further investigated items with differential item function (DIF) in the Social/Cognitive domain of a measure of everyday activity performance, the Pediatric Evaluation of Disability Inventory-Computer Adapted Test version for Autism "PEDI-CAT (ASD)," to understand possible sources of response variation in a heterogeneous sample of youth with autism compared to the national standardization sample.
  
  
  METHODS
  Cross-sectional design. A convenience sample of parents who identified they had a child between 3 and 21 years (M = 11.9 years, SD = 4.67 years) with autism (n = 365) completed an online survey that included the PEDI-CAT (ASD) and descriptive measures. For 28 items previously identified as having DIF, the PEDI-CAT (ASD) expected item score curves for the autism sample were compared to the original PEDI-CAT standardization sample. The weighted area between expected score curves (wABC) was also calculated; values >0.24 indicate significant DIF.
  
  
  RESULTS
  All items had wABC that exceeded the criterion. Compared with peers without disabilities at the same ability level, 11 items were significantly more difficult for the youth with autism and 16 items were significantly easier. One item demonstrated non-uniform DIF.
  
  
  CONCLUSIONS
  Differential responses could indicate that: (1) children with autism have a different developmental pattern of skill acquisition for everyday activities in the Social/Cognitive domain, or (2) parents of children with autism utilize a unique appraisal process when assessing their children's functional performance of everyday activities. Further research is required to better understand the factors leading to differential responses on the targeted items. The study illustrates the value of in-depth analysis of DIF to gain insight into the impact of a clinical condition on functional performance.
authors.affiliation: Ph.D. Program in Rehabilitation Sciences, Department of Occupational Therapy, Boston University, Boston, MA, 02215, USA. kramerj@bu.edu.
authors.forename: Jessica M
authors.identifier: http://orcid.org/0000-0002-3433-2842
authors.initials: JM
authors.lastname: Kramer
authors.affiliation: Ph.D. Program in Rehabilitation Sciences, Department of Occupational Therapy, Boston University, Boston, MA, 02215, USA.
authors.forename: Kendra
authors.initials: K
authors.lastname: Liljenquist
authors.affiliation: Health and Disability Research Institute, Health Policy and Management, Boston University, Boston, MA, USA.
authors.forename: Pengsheng
authors.initials: P
authors.lastname: Ni
authors.affiliation: Ph.D. Program in Rehabilitation Sciences, Department of Occupational Therapy, Boston University, Boston, MA, 02215, USA.
authors.forename: Wendy J
authors.initials: WJ
authors.lastname: Coster
mesh_terms: D000203:Activities of Daily Living / Q000523:psychology*; D001321:Autistic Disorder / Q000453:epidemiology*; D002648:Child; D003430:Cross-Sectional Studies; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D008297:Male; D011788:Quality of Life / Q000523:psychology*; D011795:Surveys and Questionnaires
keywords: Autistic disorder; Differential item function (DIF); Item response theory