Paired-samples designs are used frequently in educational and behavioral research. In applications where the response variable is quantitative, researchers are encouraged to supplement the results of a paired-samples t-test with a confidence interval (CI) for a mean difference or a standardized mean difference. Six CIs for standardized mean…

An appropriate estimate of statistical power is critical for the design of intervention studies. Although the inclusion of a pretest covariate in the test of the primary outcome can increase statistical power, samples selected on the basis of pretest performance may demonstrate range restriction on the selection measure and other correlated…

Background of Problem: Brain injury is a leading cause of death and disability in children and adolescents. According to the Brain Injury Association of America (2015) ages 0-4 and 15-19 are the two age groups at greatest risk for traumatic brain injury (TBI) or concussion. Five out of ten concussions are not reported or go undetected. The…

This article reviews all (quasi)experimental studies appearing in the first 19 volumes (1997-2015) of "Language Teaching Research" (LTR). Specifically, it provides an overview of how statistical analyses were conducted in these studies and of how the analyses were reported. The overall conclusion is that there has been a tight adherence…

Purpose: Organisations invest heavily in training and development initiatives (Miller, 2012). However, a small percentage of what is learnt by the trainees from training gets transferred to the job (Mackay, 2007). The purpose of this study is to extend previous findings and examine various organisational factors, which have not been studied…

Research by Huck and McLean (1975) demonstrated that the covariance-adjusted score is more powerful than the simple difference score, yet recent reviews indicate researchers are equally likely to use either score type in two-wave randomized experimental designs. A Monte Carlo simulation was conducted to examine the conditions under which the…

Elementary grade students in a mid-Atlantic state school district have not been meeting academic standards on state assessments. Research indicates that academic achievement is connected to self-directed readiness to learn; however, often the instruction in strategies for student self-directed readiness to learn remains teacher-centered. The…

Number relationships, which go far beyond counting skills, refer to the ability to represent a quantity in multiple, flexible ways. It is arguably among the most important mathematics concepts in number and quantity. The current study examined the effectiveness of number relationships instruction in preschool classrooms. Participants included 73…

Pretest-posttest experimental designs often are used in randomized control trials (RCTs) in the education field to improve the precision of the estimated treatment effects. For logistic reasons, however, pretest data often are collected after random assignment, so that including them in the analysis could bias the posttest impact estimates. Thus,…

Objectives: Group-randomized designs are well suited for studies of professional development because they can accommodate programs that are delivered to intact groups (e.g., schools), the collaborative nature of professional development, and extant teacher/school assignments. Though group designs may be theoretically favorable, prior evidence has…

Evaluation is an essential component of any Extension education program. One tool, the pre- and post-test, provides measurable evaluation data. Yet often the answer "I don't know" or all possible answers to a multiple choice question are not included in the repeated measure analysis. Because more than two answers are offered, the test of marginal…

Nearly 20 years of empirical work has demonstrated that cultural-asset focused learning environments can improve the academic performance of African-American students. One example is communal learning context, which shifts students' motivational primacy from the individual to the social group. Considering the critical role of efficacy beliefs in…

The American public school curriculum has narrowed as a result of the No Child Left Behind Act of 2001. Music is being eliminated in public schools so more time and resources can be spent on "tested" subjects like reading and math. However, research has shown that both the intrinsic and extrinsic values of music may improve reading…

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…