Integrated Psychometric Evaluation of the Self-Report SDQ Emotional Problems Scale Across Adolescence: Longitudinal Invariance and Item Functioning in Two Norwegian Cohorts

This repository contains Mplus and R syntax used to evaluate the structural validity and item-level properties of the SDQ Emotional Problems scale in two independent adolescent samples (Grades 8–10 and 11–13), together with the supplementary tables associated with the study. The R syntax was used to estimate separate-wave confirmatory factor analysis (CFA) models and to generate and evaluate dynamic fit-index cutoffs. The Mplus syntax was used for longitudinal CFA and measurement invariance testing across time and gender, discriminant validity analyses comparing the SDQ Emotional Problems scale with a measure of recent affective distress, and longitudinal graded response models (GRMs).