This article develops new closed-form variance expressions for power analyses for commonly used difference-in-differences (DID) and comparative interrupted time series (CITS) panel data estimators. The main contribution is to incorporate variation in treatment timing into the analysis. The power formulas also account for other key design features…

Literature addressing missing data handling for random coefficient models is particularly scant, and the few studies to date have focused on the fully conditional specification framework and "reverse random coefficient" imputation. Although it has not received much attention in the literature, a joint modeling strategy that uses random…

We demonstrate the effect of sample and trial size on statistical outcomes for single-subject analyses (SSA) and group analyses (GA) for a frequently studied performance activity and common intervention. Fifty strides of walking data collected in two blocks of 25 trials for two shoe conditions were analyzed for samples of five, eight, 10, and 12…

Despite recent emphasis on the use of randomized control trials (RCTs) for evaluating education interventions, in most areas of education research, observational methods remain the dominant approach for assessing program effects. Over the last three decades, the within-study comparison (WSC) design has emerged as a method for evaluating the…

The purpose of this study was to analyze and compare recent research papers on foreign language education in Turkish context with those published in international context to shed light on researchers and policy makers for future studies. This study filled a gap in this field and also aimed to increase the rate of acceptance of research papers…

In a randomized controlled trial, a decision needs to be made about the total number of subjects for adequate statistical power. One way to increase the power of a trial is by including a predictive covariate in the model. In this article, the effects of various covariate adjustment strategies on increasing the power is studied for discrete-time…

Despite recent shifts in research emphasizing the value of carefully designed experiments, the number of studies of teacher professional development with rigorous designs has lagged behind its student outcome counterparts. We outline a framework for the design of group randomized trials (GRTs) with teachers' knowledge as the outcome and…

With research indicating substantial differences among teachers in terms of their effectiveness (Nye, Konstantopoulous, & Hedges, 2004), a major focus of recent research in education has been on improving teacher quality through professional development (Desimone, 2009; Institute of Educations Sciences [IES], 2012; Measures of Effective…

This article reviews several decades of the author's meta-analytic and experimental research on the conditions under which nonrandomized experiments can approximate the results from randomized experiments (REs). Several studies make clear that we can expect accurate effect estimates from the regression discontinuity design, though its statistical…

Background: A meta-analysis examined the effects of deinstitutionalisation on adaptive behaviour outcomes in persons with intellectual disability. The need for an updated review in this area is reflected by recent policy shifts in community care practices and the international status of deinstitutionalisation efforts. Method: Twenty-three studies…

This methodological brief introduces the readers to the propensity score matching method, which can be used for enhancing the validity of causal inferences in research situations involving nonexperimental design or observational research, or in situations where the benefits of an experimental design are not fully realized because of reasons beyond…

This randomized controlled trial compared results obtained after 12 months of nonintensive parent training plus care-as-usual and care-as-usual alone. The training focused on stimulating joint attention and language skills and was based on the intervention described by Drew et al. (Eur Child Adolesc Psychiatr 11:266-272, 2002). Seventy-five…

Undergraduate students (N = 47), enrolled in 2 separate psychology research methods classes, evaluated a power analysis lab demonstration and homework assignment. Students attended 1 of 2 lectures that included a basic introduction to power analysis and sample size analysis. One lecture included a demonstration of how to use a computer-based power…

Data from international comparative studies in education are generally derived from complex, multi-stage sample designs and rotated assessments. Consequently, care must be taken not only in estimating variance components but also in interpreting them. Target population definitions, the nature of the sampling stages and their sampling units, and…

Current omnibus procedures for the analysis of interaction effects in repeated measures designs which contain a grouping variable are known to be nonrobust to violations of multisample sphericity, particularly when group sizes are unequal. An alternative approach is to formulate a comprehensive set of contrasts on the data which probe the specific…