Abstract
BACKGROUND: Emotional regulation is essential for mental health, cognitive development, and academic success. Existing measurement tools rely on classical test theory, limiting precision and generalizability. Most instruments also focus on specific strategies rather than capturing the multidimensional nature of emotional regulation. This study developed and validated the Emotional Regulation Inventory (ERI) using the Rasch model to ensure a psychometrically robust assessment tool for high school students. MATERIALS AND METHODS: A quantitative, cross-sectional survey was conducted in high schools across East Java, Indonesia, with 559 students (ages 14-18) from grades 10-12 participating through convenience sampling. The ERI was based on Gross's three-dimensional framework: goal activation, process engagement, and trajectory modulation. Initially containing 48 items, it was refined to 40 through expert review and pilot testing. Students responded using a four-point Likert scale. Data were analyzed using Rasch model-based psychometric testing in Winstepsoftware, assessing item fit, unidimensionality, reliability, rating scale functionality, and Differential Item Functioning (DIF). RESULTS: The ERI met unidimensionality criteria, demonstrated high reliability (person reliability = 0.89, item reliability = 0.99), and showed no significant bias across demographic groups. The Wright Map confirmed effective item distribution, ensuring precise measurement. CONCLUSION: The ERI is a valid, reliable tool for assessing emotional regulation in high school students. Findings highlight cultural and social influences, supporting its integration into school curricula. Future research should explore cross-cultural applications and their role in enhancing students' resilience and academic success.