Research questions regarding how, for whom, and where a treatment achieves its effect on an outcome have become increasingly valued in substantive research. Such questions can be answered by causal moderated mediation analysis, which assesses the heterogeneity of the mediation mechanism underlying the treatment effect across individual and…

The author describes her 30 years of experience in the design and conduct of a series of large-scale randomized controlled studies in the field of public welfare. She describes how these studies came about, what lessons can be drawn about research methods, what was learned about the effectiveness of these programs (the National Supported Work…