Data from multiple school sources, including informant ratings, systematic direct observations (SDOs), and school wide data (e.g., office disciplinary referrals [ODRs]) are routinely used to guide decision making in the delivery of evidence based practices for students with externalizing and internalizing behavior problems. Over 50 years of research show that these data sources are likely to diverge. Yet, there is little to no guidance from research about how to interpret and use these divergent data to adapt and tailor evidence based interventions for individual students. We describe how researchers can employ Kraemer et al.'s (2003) framework to guide the selection of data sources and single case design (SCD) research to analyze data from these sources. We then apply the Operations Triad Model (OTM) to interpret teacher ratings and SDOs in SCD and recommend future directions for research in behavioral decision making using multiple sources of data within SCD. [This chapter was published in: "Handbook of Special Education Research: Theory, Methods, and Developmental Processes," edited by T. Farmer, E. Talbott, K. McMaster, D. Lee, and T. Aceves, Routledge, 2022, pp. 231-244.]