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Thomas D. Cook William R. Shadish Vivian C. Wong 《Journal of policy analysis and management》2008,27(4):724-750
This paper analyzes 12 recent within‐study comparisons contrasting causal estimates from a randomized experiment with those from an observational study sharing the same treatment group. The aim is to test whether different causal estimates result when a counterfactual group is formed, either with or without random assignment, and when statistical adjustments for selection are made in the group from which random assignment is absent. We identify three studies comparing experiments and regression‐discontinuity (RD) studies. They produce quite comparable causal estimates at points around the RD cutoff. We identify three other studies where the quasi‐experiment involves careful intact group matching on the pretest. Despite the logical possibility of hidden bias in this instance, all three cases also reproduce their experimental estimates, especially if the match is geographically local. We then identify two studies where the treatment and nonrandomized comparison groups manifestly differ at pretest but where the selection process into treatment is completely or very plausibly known. Here too, experimental results are recreated. Two of the remaining studies result in correspondent experimental and nonexperimental results under some circumstances but not others, while two others produce different experimental and nonexperimental estimates, though in each case the observational study was poorly designed and analyzed. Such evidence is more promising than what was achieved in past within‐study comparisons, most involving job training. Reasons for this difference are discussed. © 2008 by the Association for Public Policy Analysis and Management. 相似文献
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Although agricultural biotechnology has been a seminal reference point in risk perception studies, public awareness of their exposure to risk deriving from this new technology has been minimal at best. However, recent events indicate there may be growing public concern as new variations of this technology appear. Understanding what drives perceptions of benefits from the third generation of the agricultural biotechnology and what determines public worries are keys for the future of this technology. To this end, this study analyzes survey data from the midsouth region of the United States to construct four separate regression models of perceived benefits from and worries over plant‐made industrial products and plant‐made pharmaceuticals. Findings suggest that while prior experience with and knowledge about agricultural biotechnology has an impact on perceptions of benefits and worries, trust in farmers plays a highly important role in determining perceptions. 相似文献
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Journal of Chinese Political Science - 相似文献
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The U.S. electric power sector has experienced a substantial shift of the generation mix since the turn of the century, moving from heavy reliance on coal‐powered generation to one drawing more from natural gas and, more recently, renewables. This transition has been forged by a mix of macroeconomic factors (recession and recovery); technological breakthroughs (horizontal drilling coupled with hydraulic fracturing; improvements in natural gas plant efficiency); clean energy policies at federal, state, and local levels of government; and private sector demands for carbon‐free energy sources. These factors have combined to reduce carbon emissions from electric power generation substantially this century. In this article we examine the extent of this transition, its causes, as well as the distinct American institutional factors steering it, including energy and environmental federalism, electoral politics, and the political economy of clean energy policy enactment and resistance. 相似文献
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