Evidence-Based Accommodations for Postsecondary Students with Disabilities: Beware the Base Rate Fallacy

Abstract

Postsecondary students with disabilities may be entitled to academic accommodations such as additional time on exams, testing in a separate setting, or course waivers and substitutions. In the past, colleges and universities relied on multi-method, multi-informant data to render accommodation decisions. Over the past decade, however, institutions have increasingly emphasized students’ self-reports over information from other sources. In this study, we examined the validity of relying primarily on self-report data to identify students with disabilities. A large, diverse sample of undergraduates with and without disabilities rated their academic functioning across multiple domains. Although students with disabilities were more likely to report impairment than students without disabilities, most students without disabilities reported at least one substantial limitation in academic functioning. Whereas the positive predictive power of students’ self-reports was low, the negative predictive power was high, indicating that students’ reports should be used to rule out disabilities rather than to identify students in need of accommodations. Adding information from other sources (e.g., school records, psychoeducational test scores) can greatly increase identification accuracy. Before granting accommodations, professionals should be mindful of the high base rate of self-reported academic problems among students without disabilities and always seek third-party data that corroborate students’ self-reports.