Item response theory (IRT) models are the main psychometric approach for the development, evaluation, and refinement of multi-item instruments and scaling of latent traits, whereas multilevel models are the primary statistical method when considering the dependence between person responses when primary units (e.g., students) are nested within…

A wide body of research has documented the relationship between social norms and individual behaviors. There is growing evidence that academic behaviors in early adolescence--when most children begin middle school--may be subject to normative influence as well. However, the structure and composition of peer relationships within middle schools have…

Mediation analysis is a statistical approach used to examine how the effect of an independent variable on an outcome is transmitted through an intervening variable (mediator). In this article, we provide a gentle introduction to single-level and multilevel mediation analyses. Using single-level data, we demonstrate an application of structural…

With increasing attention to school violence and aggression, it is argued that more covert, natured, subtle conflicts among students should be carefully examined and addressed to prevent negative outcomes. This article provides an overview of current knowledge on relational aggression including its definition, its link to a number of adjustment…