Understanding evaluations of home visitation programs.

This journal issue comprises reports concerning program evaluations of key national home visitation models. No single evaluation can answer all the questions of interest about a program, nor is any evaluation perfect, which means that readers must carefully weigh the intended purpose of the evaluation and the evaluation's strengths and weaknesses before deciding what conclusions can credibly be drawn from its results. This article begins with a discussion of the role of evaluation both in improving programs and in determining program effects. The choices required to craft a strong and methodologically rigorous evaluation are described: what outcomes to measure and how; what methods to use in designing the evaluation and building a comparison group; how many participants to enroll; and how to devise a strong plan for data analysis involving subgroups of the enrolled families. The article then discusses additional factors policymakers and practitioners should consider when interpreting the results of home visiting evaluations: attrition, the policy and functional importance of the outcomes, and the likely generalizability of the results to other communities or other populations. The evaluations that appear in this journal issue are used as examples throughout the article, and the measures that were used in those evaluations are summarized. The evaluations included in this journal issue have both strengths and weaknesses but are probably among the better evaluations in the home visiting field.