ABSTRACT
In this chapter, we present an overview of several data-related issues associated with modeling individual and group processes embedded in hierarchical data structures. We first provide an introductory discussion of the application of sample weights, focusing in particular on their potential impact at the group level of the study. Second, we turn our attention to issues related to sample size requirements in multilevel models and corresponding statistical power to detect hypothesized effects. Third, we discuss some common issues related to missing data. Finally, we conclude with some further thoughts about multilevel modeling.
