Field experiments with nested structures assign entire groups such as schools to treatment and control conditions. Key aspects of such cluster randomized experiments include knowledge of the intraclass correlation structure and the sample sizes necessary to achieve adequate power to detect the treatment effect. The units at each level of the…

As teacher professional development research includes more experimental designs, new challenges arise. We examine the threat of participant attrition as an example of the types of problems researchers face. Counter-intuitively, higher levels of recruitment effort were related to higher dropout rates among teachers. We also found that teachers left…

Background/Context: Determining the effectiveness of reform strategies is a major part of the current and future educational research agenda. Effects of education reforms will be evaluated largely quantitatively, and an important aspect of this work will be judging how well reform strategies work. The rhetoric of contemporary school reform…