Small Samples Due to Lower-Than-Planned Enrollment in Impact Evaluations: What to Do?

Impact evaluations in child welfare and other fields often struggle because of smaller-than-planned sample sizes. Multiple factors might contribute to the problem: The program’s target population might be smaller than was projected, or recruiting and enrolling eligible participants into the study might have proven unexpectedly difficult. Small sample sizes can create difficulties and limitations when estimating the impacts of programs—especially when you had not planned for them during the evaluation design phase. This brief, presented as a series of questions and answers, addresses this specific problem and offers guidance for analyzing data and reporting findings when it occurs.