Anderson, D. (2013). Hierarchical Linear Modeling (HLM): An introduction to key concepts within cross-sectional and growth modeling frameworks (Technical Report No. 1308). Eugene, OR: Behavioral Research and Teaching, University of Oregon. This manuscript provides an overview of hierarchical linear modeling (HLM), as part of a series of papers covering topics relevant to consumers of educational research. HLMis tremendously flexible, allowing researchers to specify relations across multiple “levels” of the educational system (e.g., students, classrooms, schools, etc.). TechRpt_1308