A common assumption in meta-analysis is that effect sizes are independent. When correlated effect sizes are analyzed using traditional univariate techniques, this assumption is violated. This research assesses the impact of dependence arising from treatment-control studies with multiple endpoints on homogeneity measures "Q" and…

To obtain information on the safety and efficacy of the gluten-free/casein-free (GFCF) diet, we placed 14 children with autism, age 3-5 years, on the diet for 4-6 weeks and then conducted a double-blind, placebo-controlled challenge study for 12 weeks while continuing the diet, with a 12-week follow-up. Dietary challenges were delivered via weekly…

A key issue in quasi-experimental studies and also with many evaluations which required a treatment effects (i.e. a control or experimental group) design is selection bias (Shadish el at 2002). Selection bias refers to the selection of individuals, groups or data for analysis such that proper randomization is not achieved, thereby ensuring that…

This article examines changes in the research design, sample size, and precision between the planning phase and implementation phase of group randomized trials (GRTs) funded by the Institute of Education Sciences. Thirty-eight GRTs funded between 2002 and 2006 were examined. Three studies revealed changes in the experimental design. Ten studies…

Field experiments that involve nested structures frequently assign treatment conditions to entire groups (such as schools). A key aspect of the design of such experiments includes knowledge of the clustering effects that are often expressed via intraclass correlation. This study provides methods for constructing a more powerful test for the…

This paper includes a nontechnical description of methods for calculating effect sizes in intellectual and developmental disability studies. Different hypothetical studies are used to illustrate how null hypothesis significance testing (NHST) and effect size findings can result in quite different outcomes and therefore conflicting results. Whereas…

Character education has become one of the fastest growing reform movements in K-12 education today, partially in response to unacceptable levels of student misbehavior and inadequate endorsement of good character values (Williams 2000). Between 1993 and 2009, 36 states passed laws mandating or recommending some aspect of character education in…

High-stakes assessments have encouraged educators to ignore the needs of the top performers. Therefore, the Oakwood School District decided to implement a mathematics pilot enrichment program in order to meet the needs of the advanced mathematics students. As a result, this study used quantitative data to determine if there was a significant…

In randomized controlled trials (RCTs) where the outcome is a student-level, study-collected test score, a particularly valuable piece of information is a study-collected baseline score from the same or similar test (a pre-test). Pre-test scores can be used to increase the precision of impact estimates, conduct subgroup analysis, and reduce bias…

The project reported here is conducting repeated randomized control trials of an approach to high school geometry that utilizes Dynamic Geometry (DG) software to supplement ordinary instructional practices. It compares effects of that intervention with standard instruction that does not make use of computer drawing/exploration tools. The basic…

Investigates the equality of "p" correlated effect sizes for "k" independent studies in which treatment and control groups are compared using Hotelling's "T" statistic. Illustrates the procedure and discusses the importance of sample size. (SLD)

This article discusses the circumstances under which unequal sample size in the two-group study can arise and result in an attenuated point-biserial correlation. Formulas are provided for correcting the coefficient either directly or through the mediation of relevant statistics found in studies where the coefficient itself is not reported.…

The No Child Left Behind Act (P.L. 107-110) called for the U.S. Department of Education to carry out a national study of the effectiveness of educational technology. With computers becoming ubiquitous in American schools, and purchases of hardware and software now substantial expenses for school districts, whether funding is supporting effective…