Meta-analyses are syntheses of effect-size estimates obtained from a collection of studies to summarize a particular field or topic (Hedges, 1992; Lipsey & Wilson, 2001). These reviews are used to integrate knowledge that can inform both scientific inquiry and public policy, therefore it is important to ensure that the estimates of the effect…

Randomized controlled trials (RCTs) and regression discontinuity (RD) studies both provide estimates of causal effects. A major difference between the two is that RD only estimates local average treatment effects (LATE) near the cutoff point of the forcing variable. This has been cited as a drawback to RD designs (Cook & Wong, 2008).…

Problems associated with randomization tests in single- case experiments are discussed. This article follows a discussion of randomization tests in single case studies in the same issue of this journal. (See TM 505 799; 505 801).(Author/JKS)

The selection of subjects for research on learning disabilities is a function of contemporary notions about learning disabilities, the purpose of the study and level of knowledge about the topic, and practical constraints. Denigrations of the extant research database, along with unaffordable demands for subject selection and descriptions, threaten…

Explains the characteristics and importance of random assignment in experimental research on education. Considers factors supporting causal inferences, the nature of "assignment units," differences between random sampling and random assignment, the characteristics of randomization tests, forms of random assignment, and effects of experimental…

The use of large-N group comparison research methods based on a nomothetic model is compared with idiographic methods employing single-system designs and intensive study of the individual. Limitations of the nomothetic model and advantages of the idiographic approach are presented. (SK)

The use of analysis of variance was examined under the assumption that the treatment had been randomly assigned to students, when in fact, the class had been the unit. Data support the idea that if one can randomly assign treatments to intact classes, consideration should certainly be given to doing so. (Author/GK)

Research articles published in 10 major journals during the years 1984-1987 were evaluated to determine how many satisfied the recommendations of the Council for Learning Disabilities' Research Committee on reporting subject data. Only 4 of the 277 articles included acceptable information in 7 recommended areas of subject data. (Author/JDD)

Criteria for suitable research designs for use with large databases are suggested and analyzed. The advantages and disadvantages of several types of quasi-experimental designs are compared. Examples are taken from the authors' research with data from the Manitoba Health Services Commission. (Author/AL)

A meta-analysis was conducted on 44 educational studies that used either a (labelled) Hawthorne control group, a manipulation of Hawthorne effects, or a group designed to control for the Hawthorne effect. The sample included published journal articles, ERIC documents or unpublished papers, and dissertations. The studies were coded on 20 variables,…

Studies (N=168) describing the use of behavioral interventions with behavior-disordered students were analyzed in terms of their reporting on four classes of marker variables: descriptive, substantive, topical, and background. Data showed that more thorough descriptions of research populations are required in the areas of selection criteria,…

This paper discusses the problem of vague and inconsistent descriptions of individuals with learning disabilities in research reports, presents guidelines for the description of participants in small and large sample research studies, and makes suggestions for promoting compliance with the minimum standards. (Author/JDD)

Ninety-two research reports involving specifically language-impaired subjects were reviewed. Analysis showed few consistent trends with respect to subject selection, subject description, and the number and types of control groups. The importance of more complete subject descriptions and matching criteria for control groups is discussed.…

The effects of conditions of informed consent and disclosure on the performance of 84 students doing a statistics laboratory assignment for an introductory graduate course in statistics at a state university in the southeast were studied. Four separate classes taught by three instructors were included. Subjects ranged in age from 22 to 47 years,…

Problems associated with the analysis of data collected using the Solomon Four Group Design are discussed. The design includes an experimental group and a control group that have been pretested and posttested, and an experimental and a control group that have been posttested only. A sample problem is approached in three different ways. First, the…