Multilevel Descriptive Statistics and Data Preparation // Provides tools for multilevel descriptive statistics and data preparation. Computes within-group and between-group correlations (via variance decomposition or two-level structural equation modeling), intraclass correlation coefficients (ICCs), and descriptive statistics for nested data (e.g., repeated measurements per person), supporting both frequentist (via 'lme4' or 'lavaan') and Bayesian (via 'brms') estimation. Results are formatted according to APA standards and can be exported as tables using 'gt' or 'tinytable'. Also includes functions for decomposing variables into within-group and between-group components for use in Random Effects Within- Between (REWB) models.