In this lecture Dr. Bakir Haryanto from Australian Council for Educational Research, Indonesia office, will present data analysis in large assessment scale which usually include in different level (individual and school level for instance). Multilevel data analysis is crucial in large-scale assessments, allowing examination of individual, group, and contextual factors influencing outcomes. This approach considers nested structures, such as students within classrooms or schools, providing a comprehensive understanding of diverse influences on assessment results. By accounting for hierarchical relationships, it enhances the accuracy of interpretations, identifies patterns, and informs targeted interventions. This methodology is integral for educational policymakers and practitioners, enabling nuanced insights into educational systems’ complexities, ultimately promoting effective decision-making and improving overall assessment strategies.