Generalizability theory is a psychometric framework and statistical methodology used to evaluate the dependability (reliability) of behavioral measurements. It investigates how different sources of variation, or "facets," contribute to the total variability in observed scores, enabling researchers to quantify and understand the extent to which measurement results can be generalized across various conditions (e.g., raters, items, occasions). Its significance lies in providing a comprehensive approach to measurement design and evaluation, allowing for the optimization of data collection procedures and the interpretation of measurement scores in relation to specific intended uses.