Definition x treatment interactions for students with learning disabilities

Abstract

This article investigates whether intervention outcomes for students with learning disabilities (LD) vary as a function of IQ and/or reading level. Effect sizes for 180 intervention studies were analyzed across instructional domains (e.g., reading, mathematics), and sample characteristics (e.g., intelligence, reading). The important findings were (a) a significant intelligence x reading level interaction emerges related to the magnitude of treatment outcomes indicating that studies which produced the highest effect sizes reported the smallest discrepancy between intelligence and reading (intelligence scores between 84 and 91 and reading scores between 84 and 91) when compared to other studies; (b) effect sizes were higher for strategy instruction and direct instruction-only models when studies met cut-off score criteria (study samples report standardized IQ scores at or above 85 and reading scores at or below the 25th percentile) when compared to other studies; and (c) effect sizes were more positive for a Combined Strategy and Direct Instruction model when compared to competing instructional models, but the difference in magnitude was weakened when compared to competing models when samples were defined as meeting cut-off score criteria. Overall, the results support the notion that variations in how LD samples are defined are related to the magnitude of treatment outcomes.