Comparing the Effects of Two Reading Interventions Using a Randomized Alternating Treatment Design

An emerging body of research suggests that incorporating randomization schemes in single-case research designs strengthens study internal validity and data evaluation. The purpose of this study was to test the utility and feasibility of a randomized alternating-treatment design in an investigation that compared the combined effects of vocabulary instruction and the paraphrasing strategies on expository comprehension of six students with reading difficulties. We analyzed the data using three types of randomization tests as well as visual analysis. The visual analysis and randomization tests confirmed the additional benefit of vocabulary instruction on expository comprehension for one student. However, the effects were not replicated across the other five students. We found that proper randomization schemes can improve both internal validity and data analysis strategies of the alternating-treatment design.