This digest makes the case that careful planning of replication can enhance the interpretability of applied research. When results are consistent across several studies, there is a stronger basis for observed relationships than the support that is available within each study by itself, since results that have been replicated are considered more…

This Digest provides a review and applications of the concepts of normal distribution, standard deviation, effect size, and translation of effect size into percentile gain, the foundations for the understanding of meta analytic results. Meta analysis is a statistical technique that enables the results of a number of studies to be combined to…

This digest addresses the role of evaluation and its basic logic, and provides a description of how the field is structured. In order to reach evaluative conclusions it is usually necessary to establish or identify factual promises and value premises. To obtain the required kind of overall evaluative conclusion, it is typically necessary to…

An important issue in educational and employment settings is the degree to which evidence of validity obtained in one situation can be generalized to another situation without further study of validity in the new situation. Theory, procedures, and applications concerning validity generalization are addressed. Meta-analytic techniques make possible…

Meta-analysis is a collection of systematic techniques for resolving apparent contradictions in research findings. Meta-analysts translate results from different studies to a common metric and statistically explore the relations between study characteristics and findings. Since G. Glass first used the term "meta-analysis" in 1976, it has…

Research indicates that the relationship between class size and instructional effectiveness depends on a multitude of related variables, such as age level of students, subject matter taught, and instructional methods used. Recent statistical syntheses of this research reveal that the instructional benefits of smaller classes are most significant…

This digest provides an overview of several meta-analysis studies which focused on various aspects of science instruction. These studies examined: productive factors in science learning for grades 6 through 12; quality and quantity of instruction; effects of various teaching strategies on science achievement; instructional systems in science…

The first science education digest for 1985 focused on data obtained by use of meta-analysis techniques on research studies of science instruction. Instruction seldom takes place without instructional materials, so this second digest is a companion one containing a discussion of science education research on instructional materials. Data are shown…

In an effort to provide information about the effect of computer use in schools on student achievement, attitudes, dropout rate, and learning time, a review of instructional computing research analyzed studies done between 1980 and 1987 using statistical summary procedures. Reviewers used a meta analysis procedure to calculate effect size as they…