Testing the efficacy of a tier 2 mathematics intervention: A conceptual replication study

The purpose of this closely aligned conceptual replication study was to investigate the efficacy of a Tier 2 kindergarten mathematics intervention. The replication study differed from the initial randomized controlled trial on three important elements: geographical region, timing of the intervention, and instructional context of the counterfactual. Similar to the original investigation, however, the current study tested the same intervention, used the same outcome measures and statistical analyses, and involved the same population of learners. A total of 319 kindergarten students with mathematics difficulties from 36 kindergarten classrooms participated in the study. Students who were randomly assigned to the treatment condition received the intervention in small-group formats, with 2 or 5 students per group. Control students participated in a no-treatment control condition. Significant effects on proximal and distal measures of mathematics achievement were found. Effect sizes obtained for all measures fell within or exceeded the upper bound of the effects reported in the initial study. Implications for systematically situating replication studies in larger frameworks of intervention research and reporting rates of treatment response across replication studies are discussed.