Group design research studies can provide evidence to draw conclusions about "what works," "for whom," and "under what conditions" in special education. The quality indicators introduced by Gersten and colleagues (2005) have contributed to increased rigor in group design research, which has provided substantial…

By creating and analyzing matched samples, researchers can simplify their analyses to include fewer covariate variables, relying less on model assumptions, and thus generating results that may be easier to report and interpret. When two groups essentially "look" the same, it is easier to explore their differences and make comparisons…

The present paper describes the recruitment and site selection process that has been underway since January 2011, with particular emphasis on the use of Mahalanobis distance score to determine matched pairs of sites prior to randomization to treatment and control groups. Through a systematic winnowing process, the authors found that they could…

This report summarizes the complex research literature on quantitative methods for assessing how impacts of educational interventions on instructional practices and student learning differ across students, educators, and schools. It also provides technical guidance about the use and interpretation of these methods. The research topics addressed…

In this set of four supplemental tables, the authors compare the baseline test scores of the treatment and matched control group samples observed in each year after KIPP entry (outcome years 1 to 4). As discussed in Chapter III, the authors used an iterative propensity score estimation procedure to calculate each student's probability of entering…

Randomized controlled trials in educational research tend to be small. Small trials can have large, chance, imbalances in important covariates. For studies with sample sizes greater than 50, chance imbalances can be corrected using analysis of covariance; for small trials, however, statistical power is maximized if the trial is balanced and…

Recruiting schools and kids to participate in drug prevention evaluations is no longer, if it ever was, a "done deal." Since the mid-1980s, schools have been inundated with requirements for drug programs and requests to cooperate with program evaluations. As a consequence, both treatment and control schools are harder to find. In addition, many…

Research efforts have established that the Mantel-Haenszel procedure (MHP) is an effective method for detecting the presence of test items exhibiting differential item functioning (DIF). While the MHP has been advocated for situations where item response theory based methods may not be usable, recent findings have suggested that the performance of…