The purpose of the current work is to apply several main principles of the causal explanatory approach for establishing external validity to the experimental arena. By spanning the paradigm of the experimental approach and the school of program evaluation founded by Lee Cronbach and colleagues, the authors address the question of how research…

Previous work on statistical power has discussed mainly single-level designs or 2-level balanced designs with random effects. Although balanced experiments are common, in practice balance cannot always be achieved. Work on class size is one example of unbalanced designs. This study provides methods for power analysis in 2-level unbalanced designs…

This paper analyzes 12 recent within-study comparisons contrasting causal estimates from a randomized experiment with those from an observational study sharing the same treatment group. The aim is to test whether different causal estimates result when a counterfactual group is formed, either with or without random assignment, and when statistical…

This study was made to see if there were descriptive statistics on (1) size of enrollment, (2) location (by population density), (3) availability of staff, (4) curriculum (transfer or terminal), and (5) cost per student that would predict rejection of experimental programs in staff use. The attitude of the chief administrator as the single most…

Tracking students into different classrooms according to their prior academic performance is controversial among both scholars and policymakers. If teachers find it easier to teach a homogeneous group of students, tracking could enhance school effectiveness and raise test scores of both low- and high-ability students. If students benefit from…

Summarizes evidence for the effects of class-size reduction from experimental and nonexperimental measurements, addresses questions about the robustness of each type of estimate, and suggests hypotheses that could reconcile differences resulting from conflicting evidence. Discusses potential costs and the implications for future research into the…

Participating in a research activity by volunteering in a research study or by writing a short research paper as part of a course requirement relates to favorable perceptions of psychology and research, greater knowledge of procedures associated with participation, and other demographic and situational variables. College students who volunteered…

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…

Value-added models, which rate schools for effectiveness while taking into account the poverty and other socioeconomic status of the students, are generating increased interest. This paper describes the use of one such model to evaluate whether school ratings changed when three new programs were introduced: the "Target Teach" curriculum…