Randomized trials play an important role in estimating the effect of a policy or social work program in a given population. While most trial designs benefit from strong internal validity, they often lack external validity, or generalizability, to the target population of interest. In other words, one can obtain an unbiased estimate of the study…

For the past 25 years, I have led multiple group-randomized trials, each focused on a specific underserved population of youth and each one evaluated health effects of complex interventions designed to prevent high-risk behaviors. I share my reflections on issues of intervention and research design, as well as how research results fostered my…