A cost-effectiveness analysis of classwide math intervention

Given limited resources, schools are encouraged to consider not only what works, but also at what cost. Cost-effectiveness analysis offers a formal methodology to conceptualize and calculate the ratio of the costs to implement an intervention to its effects (i.e., incremental cost-effectiveness ratios). This study used the ingredients method to analyze secondary data from a randomized controlled trial (N = 537 fourth- and fifth-grade students) to calculate the cost-effectiveness of a classwide math intervention, and provides an overview of cost-effectiveness analysis for readers unfamiliar with the formal methodology. For fourth-graders, the incremental cost-effectiveness ratio was $169.07, indicating it cost $169.07 per student for a 1 standard deviation increase in scaled scores on the state assessment. For fifth-graders, there was no statistically significant effect on the state assessment, but there were improvements in curriculum-based measurement (CBM) scores with incremental cost-effectiveness ratios ranging from $65.08 to $469.12, depending on the type of CBM probe and implementation context. Additionally, using number-needed-to-treat (i.e., the number of participants who must be provided with the intervention to prevent one failure on the state assessment), the cost was $126.90 to prevent failure on the state assessment for one fourth-grade student receiving special education services or for one student who scored below the 25th percentile on the prior year's state assessment. Implications and directions for future research are discussed.