Trends in Research on Special Needs Education:

From the Viewpoint of Internal Validity of Research Design

Abstract

  In recent years, the concept of evidence-based practice (EBP), derived from the medical field, has been spreading to the field of special support education. In this article, after discussing the concept and caveats of the evidence hierarchy in EBP, domestic research trends on special support education reported from July 2021 to June 2022 are analyzed from the perspective of the internal validity of the research design. Among intervention studies, the majority of studies with group designs used a pre-post design with low internal validity, while about half of the studies with single-case designs used a multiple baseline design with high internal validity. Single-case designs are more likely to be valid than group designs in special needs education research which has difficulties in recruiting many participants and establishing a control group. Observational studies differed across studies in whether they adequately addressed the issues of confounding variables and selection bias, regardless of the type of study design. The concept of evidence hierarchies has utility as a simplified schematic, but the importance of being aware of the concept of internal validity behind it, rather than mechanically operationalizing it, was demonstrated.