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…

Demonstration of experimental control is considered a hallmark of high-quality single-case research design (SCRD). Studies that fail to demonstrate experimental control may not be published because researchers are unwilling to submit these papers for publication and journals are unlikely to publish negative results (i.e., the file drawer effect).…

Randomized control trials are considered the gold standard for conducting research and estimating causal effects; however, educational research rarely lends itself to experimental design and true randomization. In recent years, there has been a growing interest in finding new approaches to estimate causal effects in nonrandomized studies in…

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…

Experimental designs that randomly assign entire clusters of individuals (e.g., schools and classrooms) to treatments are frequently advocated as a way of guarding against contamination of the estimated average causal effect of treatment. However, in the absence of contamination, experimental designs that randomly assign intact clusters to…

Given scarce resources for evaluation, we recommend that education researchers more frequently conduct comprehensive randomized trials that generate evidence on how, why, and under what conditions interventions succeed or fail in producing effects. Recent experience evaluating a randomized need-based financial aid intervention highlights some of…

Implementation of a guided-inquiry lab in introductory biology classes, along with scaffolded instruction, improved students' understanding of the scientific method, their ability to design an experiment, and their identification of experimental variables. Pre- and postassessments from experimental versus control sections over three semesters…

Objective: To describe promising recruitment and retention strategies for transient Latino populations, assisting investigators who work with this population in their research design and implementation. Methods: Strategies in recruitment and retention from a year-long intervention in children and their families are described. Results: Of the 159…

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…

Standardized effect sizes and confidence intervals thereof are extremely useful devices for comparing results across different studies using scales with incommensurable units. However, exact confidence intervals for standardized effect sizes can usually be obtained only via iterative estimation procedures. The present article summarizes several…

This article reports on a research effort that investigated whether the use of Microcomputer-Based Labs (MBLs), implemented within an inquiry-based activity sequence on phase transformations (melting and freezing), contributes to the development of fourth grade (9-10 year-old) students' conceptual understanding and ability to construct and…

An approach to the analysis of an aptitude-treatment-interaction (ATI) design in which the treatment groups are based on an underlying factorial structure is described and illustrated. The approach emphasizes description with point and interval estimation. The example design considered consisted of two nominal treatment variables and one interval…

The methodology suggested in this paper employs a selection rule for identifying group members that generates groups that have a range of achievement within groups but equal distribution of raw scores between. (Author/BW)

Guidelines for protection of human subjects in survey research demand that research designs provide for subjects'"informed consent." This paper reports procedures employed within a study of marijuana and other drug use which were in compliance yet avoided problems of nonparticipation and the gathering of inaccurate information. (Author)