When planning a cluster randomized trial, evaluators often have access to an enumerated cohort representing the target population of clusters. Practicalities of conducting the trial, such as the need to oversample clusters with certain characteristics in order to improve trial economy or support inferences about subgroups of clusters, may preclude…

This article describes the methodology used in the 2007 U.S. National Roadside Survey to estimate the prevalence of alcohol- and drug-impaired driving and alcohol- and drug-involved driving. This study involved randomly stopping drivers at 300 locations across the 48 continental U.S. states at sites selected through a stratified random sampling…

Complex survey data are collected by means other than simple random samples. This creates two analytical issues: nonindependence and unequal selection probability. Failing to address these issues results in underestimated standard errors and biased parameter estimates. Using data from the nationally representative Head Start Family and Child…

Thus far researchers have focused on computing average differences in student achievement between smaller and larger classes. In this study, the author focus on the distribution of the small class effects at the school level and compute the inconsistency of the small class effects across schools. The author use data from Project STAR to estimate…

Communities That Care (CTC) is a prevention system designed to reduce adolescent substance use and delinquency through the selection of effective preventive interventions tailored to a community's specific profile of risk and protection. A community-randomized trial of CTC, the Community Youth Development Study, is currently being conducted in 24…

The consent process is an integral piece of research and evaluation studies, especially when conducted within a school setting. The challenge of reaching parents of students to obtain consent is an issue with which those conducting school-based studies grapple. The literature suggests that the success of the consent process can affect the…

Previous studies have shown that active consent procedures result in sampling bias in surveys dealing with adolescent risk behaviors such as cigarette smoking and illicit drug use. To examine sampling bias from active consent procedures when the survey topic pertains to childhood obesity and associated health behaviors, the authors pair data…

Risks of life on the street caused by inclement weather, harassment, and assault threaten the unsheltered homeless population. We address some challenges of enumerating the street homeless population by testing a novel capture-recapture (CR) estimation approach that models individuals' intermittent daytime visibility. We tested walking and…

In a study of a managerial training program, two subsamples of co-workers (supervisors and subordinates) were used to validate the participants' assessments of program impact. Use of subsamples provided support in direction and magnitude of the participants' assessments and generally strengthened the validity of the findings. (TJH)

Drawing a probability sample of homeless adults in Los Angeles' Skid Row resulted in a sampling design meeting statistical criteria. The design uses data from meal centers, bed counts, and outdoor congregations; and allows unbiased estimates of prevalence of mental disorders and assessment of service needs of the homeless. (TJH)

Describes the multistage sampling system used in the 1996 national roadside survey of driver blood alcohol and compares it to the sampling methods used in prior surveys in 1973 and 1986. Although many more drivers were sampled in the most recent survey, the procedures are similar enough to allow comparison of results. (SLD)

Factors that influence the sample size necessary for longitudinal evaluations include the nature of the evaluation questions, nature of available comparison groups, consistency of the treatment in different sites, effect size, attrition rate, significance level for statistical tests, and statistical power. (Author/GDC)

Discusses ethical issues surrounding passive and active parental consent procedures when minors are to be asked sensitive research questions, exploring parental rights and the effect of active consent procedures on response rates and sample bias. Response rates are reported from two studies in which active consent procedures were implemented. (SLD)

Addressing methodological weaknesses of previous research, this study assesses whether African American women are, in fact, less likely to participate in breast cancer support groups than are White women. Of the breast cancer survivors, 958 (26% African Americans, 73% Caucasian) completed interviews concerning demographic characteristics, other…

Selectivity problems are discussed in terms of a general model that is estimated by the maximum likelihood method. Both single-group and multiple-group analyses are considered. An extension of the general model to latent variable models is discussed. (Author/PN)