In a randomized controlled trial, a decision needs to be made about the total number of subjects for adequate statistical power. One way to increase the power of a trial is by including a predictive covariate in the model. In this article, the effects of various covariate adjustment strategies on increasing the power is studied for discrete-time…

Attrition occurs when members of the initial research sample are not part of the final analysis sample, such as due to missing data or leaving the study. Both the overall sample attrition and the differences in attrition between the groups can affect the statistical equivalence of the sample and create potential for bias. The WWC has given careful…

Attrition of student affairs professionals is an issue of concern for the profession. This mixed methods study highlights reasons why participants left their student affairs careers. Seven general themes emerged from the study, including burnout, salary issues, career alternatives, work/family conflict, limited advancement, supervisor issues and…

In recent years, underserved communities have received much attention within the field of positive youth development (PYD). While there are an increasing number of opportunities for underserved youth to join PYD-based programs, there is growing concern surrounding the lack of critical evaluation of these programs (Kidd, 2008). Unfortunately, there…

As any empirical method used for causal analysis, social experiments are prone to attrition which may flaw the validity of the results. This article considers the problem of partially missing outcomes in experiments. First, it systematically reveals under which forms of attrition--in terms of its relation to observable and/or unobservable…

Recruitment and retention of research participants is evolving with the changing demographics of the American population, in particular its growing diversity. The cultural-historical background and sociopolitical conditions of each diverse group poses unique challenges in developing successful recruitment and retention methods and strategies. This…

Despite decades of policy intervention to increase college entry among low-income students, substantial inequalities in college going by family income remain. Policy makers have largely overlooked the summer after high school as an important time period in students' transition to college. During the post-high school summer, however, students must…

New professionals in student affairs enter the field motivated and ready to start their new careers (Olyha, 2004), though 50-60% of new professionals end up leaving the field before they complete their fifth year of employment (Renn & Hodges, 2007). Mentoring is a suggested strategy to help with retaining professionals in the workplace…

The past decade has seen a noticeable shift in missing data handling techniques that assume a missing at random (MAR) mechanism, where the propensity for missing data on an outcome is related to other analysis variables. Although MAR is often reasonable, there are situations where this assumption is unlikely to hold, leading to biased parameter…

Background: Social experiments frequently exploit data from administrative records. However, most administrative data systems are designed to track earnings or benefit payments among residents within a single state. When an experimental participant moves across state lines, his entries in the data system of his state of origin consist entirely of…

The purpose of this dissertation was to identify factors that contribute to the attrition of new professionals in the field of student affairs. Student affairs professionals report low levels of commitment to the field and depart from the field at rates ranging from 32% to 61% (Holmes, Verrier, & Chrisholm, 1983; Rosen et al., 1980; Rosser…

Background: Epidemiological information on age-related cardiovascular disease in people with intellectual disability (ID) is scarce and inconclusive. We compared prevalence and incidence of cerebrovascular accident and myocardial infarction over age 50 in a residential population with ID to that in a general practice population. Method: Lifetime…

Childhood obesity is one of the most serious challenges of the 21st century and it is vital that evidence-based treatment approaches can be translated into practice to meet public health needs. Yet policy-makers cannot afford to wait for the results of lengthy trials before "probably efficacious" interventions are made available to the public, and…

Researchers and evaluators have encountered a number of challenges in conducting empirically-rigorous research within juvenile correctional facilities. The purpose of this guide is to provide new researchers and evaluators with an overview of the possible challenges they may encounter when conducting research in juvenile correctional facilities so…

This addendum to previously published results presents alternative analyses of data from large-scale effectiveness studies of Cognitive Tutor Algebra I in middle schools and high schools. These alternative analyses produce results that are substantively the same as previously reported. We find a significant positive effect of 0.21 standard…