Medical students must understand statistical reasoning and sample size selection to design and interpret clinical trials. Beyond achieving sufficient statistical power, ensuring meaningful precision in treatment effect estimates is equally important. We developed free, interactive Shiny/R tools that let learners explore how varying sample sizes…

A key issue in quasi-experimental studies and also with many evaluations which required a treatment effects (i.e. a control or experimental group) design is selection bias (Shadish el at 2002). Selection bias refers to the selection of individuals, groups or data for analysis such that proper randomization is not achieved, thereby ensuring that…

Using exogenous characteristics to identify endogenous subgroups, the approach discussed in this method note creates symmetric subsets within treatment and control groups, allowing the analysis to take advantage of an experimental design. In order to maintain treatment--control symmetry, however, prior work has posited that it is necessary to use…

This article examines changes in the research design, sample size, and precision between the planning phase and implementation phase of group randomized trials (GRTs) funded by the Institute of Education Sciences. Thirty-eight GRTs funded between 2002 and 2006 were examined. Three studies revealed changes in the experimental design. Ten studies…

The continuous change characterizing 21st century society has significant implications for higher education. Educators and business leaders increasingly recognize that education within and preparation for a context of change requires learning environments fostering openness, flexibility, and engagement with other ideas and people. Such…

This article reviews several decades of the author's meta-analytic and experimental research on the conditions under which nonrandomized experiments can approximate the results from randomized experiments (REs). Several studies make clear that we can expect accurate effect estimates from the regression discontinuity design, though its statistical…

This article summarizes the creation and implementation of a concurrent support class for TRS 92--Intermediate Algebra, a developmental mathematics course at Fort Lewis College in Durango, Colorado. The concurrent course outlined in this article demonstrates a statistically significant increase in student success rates since its inception.…

Recent overviews of autism research have yielded a number of suggestions, including: additional research with very young, and with lower functioning samples, and renewed emphasis on appropriate comparison/control groups. We reviewed the abstracts from a major autism conference (IMFAR) from 2004 to 2006 to examine these trends. We found an increase…

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 study explored the influence of strengths-based development on leadership practices among undergraduate college students while controlling for gender, years of leadership experience, and number of completed leadership courses using a quasi-experimental approach with a randomized control-group pretest-posttest research design. The sample…

Parametric analysis of covariance was compared to analysis of covariance with data transformed using ranks. Using a computer simulation approach the two strategies were compared in terms of the proportion of Type I errors made and statistical power when the conditional distribution of errors were: (1) normal and homoscedastic, (2) normal and…

Expresses the importance of scientifically based research in education reform and explains how to judge the validity of educational research. Describes control groups, randomized and matched experiments, statistical educational significance, sample size, and the difference between scientifically based and rigorously evaluated research. (Contains…

Introduction: The objectives of continuing medical education (CME) programs include knowledge acquisition, skill development, clinical reasoning and decision making, and health care outcomes. We conducted a yearlong medical education research study in which knowledge acquisition in our CME programs was assessed. Method: A randomized…

This report summarizes the National Job Training Partnership Act (JTPA) Study, which examined the impact of Title IIA of JTPA on participants' employment, earnings, and welfare receipt. Between 1987 and 1989, more than 20,000 adults and out-of-school youths who applied for JTPA services in 16 areas across the country were randomly assigned to a…

Problems with conducting randomized field experiments in education are explored. Focus is on problems encountered while evaluating a group of dropout prevention projects. Project planners were asked to manipulate the subject eligibility criteria until they identified as eligible three to four times as many students as they could serve. They were…