Randomized experiments are desirable but not always possible for social policy research, so "quasi-experiments" have become popular alternatives. This article reports on a systematic review of nearly three decades of methodological research to address the question of whether there is evidence...

Reports initial findings from a synthesis and reanalysis of all available evidence on whether quasi-experimental evaluation designs produced unbiased estimates of the impacts of education, training, and welfare programs. This methodological paper tries to understand conditions under which...