Randomization of large number of participants to different treatment groups is often not a feasible or preferable way to answer questions of immediate interest to professional practice. Single case designs (SCDs) are a class of research designs that are experimental in nature but require only a few participants, all of whom receive the…

The What Works Clearinghouse (WWC) Standards Briefs explain the rules the WWC uses to evaluate the quality of studies for practitioners, researchers, and policymakers. This brief explains what baseline equivalence is and why it matters. As part of the WWC review process for certain types of studies, reviewers assess whether the intervention group…

E-learning research is plenty of difficulties, as also research in education is. Usually, the high number of features involved in e-learning processes complicates and masks the identification and isolation of the factors which cause the expected benefits, when they exist. At the same time, a bunch of threats are ready to weaken the validity of the…

This paper describes an alternative to unrestricted randomization in experimental design, termed minimization, which can be used to achieve better balance of critical factors in small to medium-sized experimental studies. Several critical factors are controlled which are known to influence outcomes but which are not the foci of the study. Based on…

This addendum to previously published results presents alternative analyses of data from large-scale effectiveness studies of Cognitive Tutor Algebra I in middle schools and high schools. These alternative analyses produce results that are substantively the same as previously reported. We find a significant positive effect of 0.21 standard…

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…

The aim of this paper is to describe a digital game with an educational purpose in the subject of computer programming, which enables students to reinforce and improve their abilities on the concepts of sequencing, defined iteration and nesting. For its design, a problem solving approach was followed and a score comparing mechanism was implemented…

Through a synthesis of test publisher norms and national longitudinal datasets, this study provides new national norms of academic growth in K-12 reading and math that can be used to reinterpret conventional effect sizes in time units. We propose d' a time-indexed effect size metric to estimate how long it would take for an "untreated"…

Experimental designs are distinguished as the best method to respond to questions involving causality. The purpose of the present paper is to explicate the logic of experimental design and why it is so vital to questions that demand causal conclusions. In addition, types of internal and external validity threats are discussed. To emphasize the…

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)

Toddlers in the lowest 10th percentile for lexical production were compared with age- and language-matched controls on measures of phonetic complexity, lexical development, and grammatical complexity. Results indicate an overlap between phonology, lexicon, and grammar and suggest the importance of true consonant production for lexical development.…

Provided in this document are the text of H.R. 4971, a record of testimony offered in a congressional hearing, and a wide variety of supplemental materials. H.R. 4971 is a bill to amend the Juvenile Justice and Delinquency Prevention (JJDP) Act of 1974 to authorize appropriations for fiscal years 1985 through 1989 and for other purposes. Numerous…