Background: Randomized controlled trials (RCTs), or experiments, are the gold standard for intervention evaluation. However, the main appeal of RCTs--the clean identification of causal effects--can be compromised by interference, when one subject's actions can influence another subject's behavior or outcomes. In this paper, we formalize and study…

Developing models and using mathematics are two key practices in internationally recognized science education standards, such as the Next Generation Science Standards (NGSS). However, students often struggle with these two intersecting practices, particularly when developing mathematical models about scientific phenomena. Formative…

Randomized experiments are commonly used to evaluate the effectiveness of educational interventions. The goal of the present investigation is to develop small-sample corrections for multiple contrast hypothesis tests (i.e., F-tests) such as the omnibus test of meta-regression fit or a test for equality of three or more levels of a categorical…

Using meta-analytic techniques this study examined the effects of applying mathematical modelling to support student math knowledge acquisition at the high school and college levels. The research encompassed experimental studies published in peer-reviewed journals between January 1, 2000, and February 27, 2013. Such formulated orientation called…

This article focuses on a method of policy analysis that has evolved from the previous articles in this issue. The first section, "Toward a Theory of Educational Production," identifies concepts from science and achievement production to be incorporated into this policy analysis method. Building on Kuhn's (1970) discussion regarding paradigms, the…

In most school achievement research, the relationships between achievement and explanatory variables follow the Newton and Einstein concept/principle and the viewpoint of the macro-observer: Deterministic measures based on the mean value of a sufficiently large number of schools. What if the relationships between achievement and explanatory…

This study uses simulation techniques to examine the statistical power of the group- randomized design and the matched-pair (MP) randomized block design under various parameter combinations. Both nearest neighbor matching and random matching are used for the MP design. The power of each design for any parameter combination was calculated from…

Cohen Kadosh, Tzelgov, and Henik [Cohen Kadosh, R., Tzelgov, J., & Henik, A. (2008). A synesthetic walk on the number line: The size effect. "Cognition", 106, 548-557] present a new paradigm to probe properties of the mental number line. They describe two experiments which they argue to be inconsistent with the exact small number model proposed by…

Accuracy is often analyzed using analysis of variance techniques in which the data are assumed to be normally distributed. However, accuracy data are discrete rather than continuous, and proportion correct are constrained to the range 0-1. Monte Carlo simulations are presented illustrating how this can lead to distortions in the pattern of means.…

Total, direct, and indirect effects in linear structural equation models are examined. Formulas currently given for direct and total effects are reported, and causation is considered. It is concluded that in many instances the effects do not support the interpretations given in the literature. (SLD)

Relationships among the noncentrality parameter for the "F" distribution, mean square between and within groups, and effect size are examined. (Author)

Notes that because estimates of effect sizes are often either misreported or not reported at all, meta-analysts must use conversion formulas that allow estimates of effect sizes from information available. Focuses on formulas that convert "F" in ANOVA, a statistical test, to eta-squared, "d," or the correlation equivalent. Demonstrates that the…

Modeling the process by which participants are selected into groups, rather than adjusting for preexisting group differences, provides the basis for several new approaches to the analysis of data from nonrandomized studies. Econometric approaches, the propensity scores approach, and the relative assignment variable approach to the modeling of…

Recommends that analysts (1) use conventional meta-analytic statistics when testing for moderator variables; (2) perform tests between mean effect sizes; and (3) continue to perform model tests in meta-analyses for which study outcomes are already consistent if they have theoretical expectations about moderators. (RS)

Several metanalytic studies of group variability use variance ratios as measures of effect size. Problems with this approach are discussed, including limitations of using means and medians of ratios. Mean logarithms and the geometric mean are not adversely affected by the arbitrary choice of numerator. (SLD)