Because studies examining youth drug use often have data with a high proportion of zeros, they often do not meet the assumptions for univariate or linear regression analyses that are typically used. We demonstrate the use of zero-inflated negative binomial regression models to address excessive zeros in drug use frequency on perceptions of…

Several methods for testing mediation hypotheses with 2-level nested data have been proposed by researchers using a multilevel modeling (MLM) paradigm. However, these MLM approaches do not accommodate mediation pathways with Level-2 outcomes and may produce conflated estimates of between- and within-level components of indirect effects. Moreover,…

Although definitions of validity have evolved considerably since L. J. Cronbach and P. E. Meehl's classic (1955) review, contemporary validity research continues to emphasize correlational analyses assessing predictor-criterion relationships, with most outcome criteria being self-reports. The present article describes an alternative way of…

The Department of Health in England released a new health research strategy in 2006 with far-reaching implications for both health research and research management. The explicit policy shift is towards centres of excellence and away from historical block allocations of funding to National Health Service (NHS) healthcare organisations--with these…

"Theory and Method in Higher Education Research" contains contemporary contributions to international debates regarding the application and development of theory and methodology in researching higher education. Higher education research is a developing field internationally, which is attracting more and more researchers from a great…

Purpose: The success of schools fundamentally depends on teachers' willingness to go above and beyond the call of duty, namely, to exhibit organizational citizenship behaviors (OCBs). Attempts to understand the causes of OCB frequently focus on individual characteristics; only recently have researchers begun to direct their attention to more…

This analysis of Zipf's law uses an index for the sequence of observed values of the variables in a Zipf-type relationship. Three important properties relating rank, count, and frequency are identified, shapes of Zipf-type curves are described, and parameters of the Mandelbrot-Zipf law are discussed. (Author/LRW)

Examines two classes of production functions in which the long-run competitive equilibrium scale of the firm increases when the relative price of the dominant factor decreases. Compares these with a third class of production functions where the equilibrium scale is independent of the relative price of the dominant factor. (MJP)

Predictors of language production skills were evaluated in 48 children and adolescents with Down syndrome and compared to 48 children matched for nonverbal mental age and mother's years of education. Comparison of two models found the model that incorporated comprehension performance (as well group membership, chronological age, cognition,…

This document reports on a study undertaken to identify specific behaviors of secondary school principals that are effective or ineffective in promoting positive school characteristics. The researchers first searched the literature to find an organizational model that would take into account the organization's goals, the means for measuring…

Described in the context of a computer simulation are highlights of a program of research focusing on the storage of mathematics problem solving information in young children's memory and the development of such knowledge structures in older children. Specifically discussed are the problem size effect, the network nature of the memory…

The overidentification of structural equation models with latent variables is discussed. The use of two- and three-indicator models is not recommended since such models do not allow a testing of the crucial assumption of unidimensionality among indicators in most cases. Models with four or more indicators may be more sensitive to departures from…

The purpose of the School Improvement Model (SIM) Project is to investigate the links between systematically developed teacher performance evaluation, administrator performance evaluation, staff development interventions, and the quality of education as measured by student achievement results. Following the 4th year of the 5-year study,…

Poor health has been implicated as a suppressor of the life satisfaction of older adults. To clarify the contribution of arthritis to this process, functional disability, negative affect, pain, current severity of the disease, self-esteem, perception of general health, and internal health locus of control, were placed within a causal model as…

Explores whether transactional/interactional, environmental, or developmental status models best represent growth from infancy to early childhood. Attempts to identify features of the social environment important for specific developmental outcomes. Observations of interactions between 40 mothers and their three-month-old infants were used to…