Project Summary/Abstract The proposed K01 Mentored Research Scientist Development Award will prepare Manshu Yang, Ph.D. to become an independent researcher in developing cutting-edge and practical statistical methodology to address the timely issue of missing data in drug use and addiction (DUA) research. Dr. Yang is currently an Assistant Professor of Quantitative Health Psychology at the University of Rhode Island. The outlined proposal builds upon her training and research experience in statistics and psychology and will facilitate her path to become a scholar dedicated to bridging state-of-the-art methodologies and substantive theory to advance knowledge of DUA etiology and intervention strategies. DUA has a myriad of deleterious impacts and continues to raise public health concerns in the US. In the past two decades, ecological momentary assessment (EMA) has been increasingly used to help researchers understand the influence of psychosocial and contextual factors on substance use in the real world and nearly in real time, so that more efficacious interventions can be developed accordingly. However, along with the opportunity of using EMA comes a significant methodological challenge: missing responses are inevitable, often substantial, and not properly handled in data analysis, hence significantly increasing researchers’ risks of reaching incorrect conclusions and developing ineffective or even unsafe interventions. Current methods cannot address all the unique methodological challenges in DUA EMA studies due to their complex missing data patterns and untestable missing data assumptions. On the other hand, EMA brings a unique opportunity to address these challenges by re-prompting participants shortly after they missed an EMA survey to retrieve their data. Such later-retrieved data are readily available from existing data (e.g., morning reports capturing missed DUA consequences in the prior day) or can be easily added to an automated EMA system without altering EMA schedule. The outlined proposal includes a comprehensive mentorship and didactic plan to support Dr. Yang’s career development and advance her knowledge and skills in DUA etiology/intervention, EMA design, data management, and analysis, Bayesian missing data analysis, and statistical programming. Specifically, the aims of the proposed research study are (1) to use all available data (initially observed and later retrieved) to characterize missing data mechanisms in DUA EMA, (2) to develop a novel Bayesian method for handling missing data and making valid inference on DUA etiology, (3) to develop a Bayesian sensitivity analysis method to test the robustness of findings to possible departures from missing data assumptions. The proposed study will investigate missing data issues and develop analysis methods using empirical EMA datasets from three NIDA-funded projects and computer- simulated data in a cost-effective way. Statistical methods developed from the study will greatly help re...