Date of Award


Document Type


Degree Name


Organizational Unit

Morgridge College of Education

First Advisor

Kathy E. Green, Ph.D.

Second Advisor

Karen Riley

Third Advisor

Monica Martinussen

Fourth Advisor

Nicholas Cutforth

Fifth Advisor

Antonio Olmos-Gallo

Sixth Advisor

Donald Bacon


Accommodations, Differential boost, High-stakes test, Meta-analysis, Meta-regression, Students with disabilities


Test accommodations are designed to ensure the comparability of test scores between students and their typically developing counterparts by eliminating as much construct-irrelevant variance and construct-irrelevant difficulty as possible. Although those involved in test creation endeavor to create tests with suitable accommodations for students with disabilities, there is lack of consensus regarding accommodation efficacy. Using meta-analysis and meta-regression to summarize previous research, this study examined whether test accommodations differentially boost test scores of students with disabilities, and whether accommodated conditions provided a more effective and valid assessment of students with disabilities. Results from the meta-analysis of 34 studies (119 effect sizes) lend support to the differential boost hypotheses, whereby students with disabilities (mean effect size = 0.30, k = 62, p < 0.001) are positively impacted by test accommodations while their typically developing peers (mean effect size = 0.17, k = 57, p < 0.001) gain little from test accommodations.

Presentation assessment accommodations (mean effect size = 0.22, k = 41, p < 0.001) had a small statistically significant impact on the performance of students with disabilities, while use of timing/scheduling accommodations (mean effect size = 0.47, k = 17, p < 0.001) had a small, bordering on medium, statistically significant impact on these students. The effect for presentation accommodations intensified when narrowing the focus to students with learning disabilities (mean effect size = 0.36, k = 23, p < 0.001) but not for timing/scheduling accommodations (mean effect size = 0.48, k = 13, p < 0.001). Overall results for setting (k = 1) and response (k = 3) accommodations were not available as there were too few studies for an overall comparison.

The results of meta-regression analyses examining the effects of assessment accommodations on test scores for students with disabilities showed that 42% of the heterogeneity in test score could be explained by an overall model examining population description, test characteristic, results dissemination, and researcher-manipulated (test accommodation effect size for students with disabilities) variables. Population description and test characteristic variable sets explained the greatest amounts of variability for mean increase in test score, R2=0.22 and R2 =0.35 respectively; researcher-manipulated variable (test accommodation) and research dissemination explained little variance, R2 =0.07 and R2 =0.01, respectively.

Publication Statement

Copyright is held by the author. User is responsible for all copyright compliance.

Rights Holder

Michelle Vanchu-Orosco


Received from ProQuest

File Format




File Size

375 p.


Educational tests & measurements, Special education