In the "individually randomized group treatment" (IRGT) experimental design, individuals are first randomly assigned to a treatment arm or a control arm, but then within each arm, are grouped together (e.g., within classrooms/schools, through shared case managers, in group therapy sessions, through shared doctors, etc.) to receive…

Using exogenous characteristics to identify endogenous subgroups, the approach discussed in this method note creates symmetric subsets within treatment and control groups, allowing the analysis to take advantage of an experimental design. In order to maintain treatment--control symmetry, however, prior work has posited that it is necessary to use…

This three-volume report describes the "SAM (School Administration Manager) process," an approach that about 700 schools around the nation are using to direct more of principals' time and effort to improve teaching and learning in classrooms. Research has shown that a principal's instructional leadership is second only to teaching among…

The authors' purpose was to explore the effects of a supplementary, guided, silent reading intervention with 80 struggling third-grade readers who were retained at grade level as a result of poor performance on the reading portion of a criterion referenced state assessment. The students were distributed in 11 elementary schools in a large, urban…

It is widely known that there is a dearth of education research in South Africa which takes as its methodological basis experimentation. The emphasis has been on educators' and learners' experiential understanding in the first decade of democracy after apartheid, when qualitative research predominated. The article investigates, first, the extent…

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…

A method is proposed for calculating the sample size needed to achieve acceptable statistical power with a given test. The minimally important difference significant (MIDS) criterion for sample size is explained and supported with recommendations for determining sample size. The MIDS criterion is computationally simple and easy to explain. (SLD)

This article considers various kinds of probability and non-probability samples in both experimental and survey studies. Throughout, how a sample is chosen is stressed. Size alone is not the determining consideration in sample selection. Good samples do not occur by accident; they are the result of a careful design. (Author/JAZ)

An evaluation of the rules-of-thumb used to determine the minimum number of subjects required to conduct multiple regression analyses suggests that researchers who use a rule of thumb rather than power analyses trade simplicity of use for accuracy and specificity of response. Insufficient power is likely to result. (SLD)

This report summarizes the National Job Training Partnership Act (JTPA) Study, which examined the impact of Title IIA of JTPA on participants' employment, earnings, and welfare receipt. Between 1987 and 1989, more than 20,000 adults and out-of-school youths who applied for JTPA services in 16 areas across the country were randomly assigned to a…

Problems with conducting randomized field experiments in education are explored. Focus is on problems encountered while evaluating a group of dropout prevention projects. Project planners were asked to manipulate the subject eligibility criteria until they identified as eligible three to four times as many students as they could serve. They were…

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…

The National Job Corps Study was conducted in 1994-1996 to provide a thorough and rigorous assessment of the impacts of the Job Corps on key participant outcomes. To ensure that the study was well implemented, a study team from Mathematica Policy Research, Inc., (MPR) investigated outcome and admission (OA) procedures in each Job Corps region and…