American Education Research Changes Tack
探讨美国教育研究从偏好定性分析转向重视随机实验的变革，梳理其思想与立法根源，并用一项随机激励实验说明新方法如何回应伦理与实践质疑，最后对加州缩小班级规模的尝试提出警示。
For a quarter century, American education researchers have tended to favour qualitative and descriptive analyses over quantitative studies using random assignment or featuring credible quasi-experimental research designs. This has now changed. In 2002 and 2003, the US Department of Education funded a dozen randomized trials to evaluate the efficacy of pre-school programmes, up from one in 2000. In this essay, I explore the intellectual and legislative roots of this change, beginning with the story of how contemporary education research fell out of step with other social sciences. I then use a study in which low-achieving high-school students were randomly offered incentives to learn to show how recent developments in research methods answer ethical and practical objections to the use of random assignment for research on schools. Finally, I offer a few cautionary notes based on results from the recent effort to cut class size in California.