The Institute of Education Sciences has funded more than 100 experiments to evaluate educational interventions in an effort to generate scientific evidence of program effectiveness on which to base education policy and practice. In general, these studies are designed with the goal of having adequate statistical power to detect the average…

The authors examined 2 approaches for determining the required sample size of Welch's test for detecting equality of means when the greatest difference between any 2 group means is given. It is shown that the actual power obtained with the sample size of the suggested approach is consistently at least as great as the nominal power. However,…

The sample size determination is an important issue for planning research. However, limitations in size have seldom been discussed in the literature. Thus, how to allocate participants into different treatment groups to achieve the desired power is a practical issue that still needs to be addressed when one group size is fixed. The authors focused…

The authors examined the robustness of multilevel linear growth curve modeling to misspecification of an autoregressive moving average process. As previous research has shown (J. Ferron, R. Dailey, & Q. Yi, 2002; O. Kwok, S. G. West, & S. B. Green, 2007; S. Sivo, X. Fan, & L. Witta, 2005), estimates of the fixed effects were unbiased, and Type I…

There is general agreement that meta-analysis is an important tool for synthesizing study results in quantitative educational research. Yet, a shared feature of many meta-analyses is a failure to report sufficient information for readers to fully judge the reported findings, such as the populations to which generalizations are to be made,…

The authors examined the use of effect sizes across an entire field, satisfying a goal J. Cohen (1997) suggested. They analyzed the extent to which researchers had reported effect sizes in the 5 major journals on gifted education between 1996 and 2005 and compiled data on the types of manuscripts published, whether researchers reported effect…

Federal standards established in 1997 allow respondents to select multiple-race categories. These new standards changed the single-race subgroup definitions that the government has required since 1977. Meta-analysis, research on long-term assessment trends, and other research involving historical comparisons must account for the definitional…

Complex survey designs often employ multistage cluster sampling designs and oversample particular units to ensure more accurate population parameter estimates. These issues must be accommodated in the analysis to ensure accurate parameter estimation. Incorporation of sample weights in some statistical procedures has been studied. However, research…

Propensity score analysis is one statistical technique that can be applied to observational data to mimic randomization and thus can be used to estimate causal effects in studies in which the researchers have not applied randomization. In this article the authors (a) describe propensity score methodology and (b) demonstrate its application using…

To deal with nonnormal and heterogeneous data for the one-way fixed effect analysis of variance model, the authors adopted a trimmed means method in conjunction with Hall's invertible transformation into a heteroscedastic test statistic (Alexander-Govern test or Welch test). The results of simulation experiments showed that the proposed technique…

Classification studies are important for practitioners who need to identify individuals for specialized treatment or intervention. When interventions are irreversible or misclassifications are costly, information about the proficiency of different classification procedures becomes invaluable. This study furnishes information about the relative…

The purpose of this study was to investigate the effects of retroactive and focused self-monitoring, actualized by videotaping, on children's theater performance. In Experiment 1, 20 students in a theater performance program were randomly assigned to either a control or a self-monitoring condition, and their weekly rehearsals were videotaped. Only…

The authors investigated the microlevel processes of collaborative reasoning in heterogeneous peer dyads working on an open-design task in elementary geometry. Special attention was paid to the nature of student social interaction, problem-solving strategies, and mathematical language and how they shape collaborative problem-solving processes.…

The authors investigated the influence of effect size and comment inclusion on readers' perceptions of research results. In three experiments, undergraduates, graduates, and faculty read a journal article that either included or did not include an effect size and commentary about the effect size. Contrary to a previous study by Robinson, Fouladi,…

The authors assessed the extent to which a generative prereading activity known as Story Impressions (SI), or composing a guess from clues, influences passage recall relative to a more passive prereading activity of reading a Content Preview (CP). The results from 74 eighth-grade students indicated the CP groups equaled the reading-only control…