Meta-studies are often conducted on empirical findings obtained from overlapping samples. Sample overlap is common in research fields that strongly rely on aggregated observational data (eg, economics and finance), where the same set of data may be used in several studies. More generally, sample overlap tends to occur whenever multiple estimates…

Outdoor adventure education (OAE) has a long history of being credited with the personal and social development (PSD) of its participants. PSD is notoriously difficult to measure quantitatively, yet stakeholders demand statistical evidence that given approaches to eliciting PSD are effective in their methods. Rightly or wrongly, many stakeholders…

If the quantitative result of a study is observed only when the mean difference is statistically significant, the observed mean difference, variance, and effect size are biased estimators of corresponding population parameters. The exact distribution of sample effect size and the maximum likelihood estimator of effect size are derived. (Author/BW)

Rosenthan's (1979) concept of fail-safe N has thus far been applied to probability levels exclusively. This note introduces a fail-safe N for effect size. (Author)

Monte Carlo studies explored the sampling characteristics of Cohen's d and three approximations to Cohen's d when used as average effect size measures in meta-analysis. Reviews of 10, 100, and 500 studies (M) were simulated, with degrees of freedom (df) varied in seven steps from 8 to 58. In a two independent groups design, samples were obtained…

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 The sample included published journal articles, ERIC documents or unpublished papers, and dissertations.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,…

The purpose of this study was to determine the types of research methods used to study cognitive processing development in gifted learners, from 1975-1986. Of 870 research publications identified on giftedness, 522 publications (60 percent) dealt with cognitive processing development. Research designs used most frequently were causal-comparative,…

Because research synthesis enables one to determine either the overall effectiveness of a particular treatment or the relative effectiveness of different types of treatments, it is becoming increasingly popular as a tool in program evaluation. Numerous methodological problems arise, however, when research synthesis is applied to studies conducted…

The implementation of research design in studies on substance abuse education is discussed in this meta-analysis. Findings indicate that the quality of research design is constrained by negative feedback from evaluation stakeholders. This finding is applied to an evaluation of the Here's Looking at You, 2000 drug education program currently…