Differential Item Functioning Analysis of ASKSP-R with School Psychologists and Speech-Language Pathologists

The current study aims to expand on existing psychometric information related to the Autism Spectrum Knowledge Scale Professional Version-Revised (ASKSP-R; McClain et al., 2019). Specifically, the study addresses two research questions: (1) Which items on the ASKSP-R show evidence of differential item functioning (DIF) between school psychologists (SPs) and speech-language pathologists (SLPs)? and (2) To what extent do ASKSP-R score distributions differ between SPs and SLPs?

Differential item functioning analysis was used to assess whether items in the measure function similarly across two groups with comparable levels of autism knowledge. Data were collected as part of a larger project examining the current state of autism knowledge among school-based professionals that frequently work with autistic children. The sample included in the study consisted of School Psychologists (n = 210) and Speech-Language Pathologists (n = 202) who completed a demographic questionnaire and the ASKSP-R measure.

Results indicated that two items (14 & 15) functioned differently across the two professional groups.

Potential explanations for item bias are discussed pertaining to training differences and focus of knowledge areas, along with suggestions for revising the measure.