evidence to the policy maker, and thus the evidence-based approach places a premium on improving policy-relevant research, often through the use of RCFTs.

In the settings in which they are carried out, RCFTs provide a strong, if not the strongest, form of scientific evidence of cause and effect. Circumstances may permit such experiments in a desired setting, such as when scarce resources are allocated by lottery, for example with admission to magnet schools or charter schools or the allocation of health care resources. An example of the latter is the Oregon Health Insurance Experiment in which names were drawn by lottery for the state’s Medicaid program for low-income, uninsured adults (Finkelstein et al., 2012).

Even when RCFTs are conducted in one setting, inference from them may be applied to other settings or contexts with concurrent collection of information on other variables or factors that differ in different settings and that may influence the results. So-called substitutes for randomized trials, however, such as “natural” experiments and “quasi-experiments,” as Sims (2010) argues, are not actually experiments. They are often invoked as a way to avoid confronting “the complexities and ambiguities that inevitably arise in nonexperimental inference.” For these situations and even in conjunction with randomized experiments, there are nonexperimental methods of drawing causal inferences and model-based methods for adjusting experimental results for inherent biases. Appendix A provides a review of some of these research methods and sets them in the context of the varied statistical methods for research and evaluation.

The active debate regarding the appropriate methodology for a given research question promotes attention in the policy community to the desirability of producing the best possible evidence under a given set of circumstances, especially the strongest evidence that bears on policy implementation and policy consequences. Bringing attention to the importance of strong evidence in policy making advances the goal of using science even though the specific formulation of an evidence-based policy approach offers little insight into the conditions that bring about its use.


Despite their considerable value in other respects, studies of knowledge utilization have not advanced understanding of the use of evidence in the policy process much beyond the decades-old National Research Council (1978) report. The family of suggestive concepts, typologies, and frame-

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