His work centers on the development of statistical methods for causal inference and impact evaluation to advance research in health care and public policy. In his methodological work, Dr. Zubizarreta uses tools from modern optimization to develop new matching and weighting methods for causal inference as alternatives to commonly used regression methods. In his health care work, he is interested in assessing the quality of care provided by hospitals and physicians using health outcomes and operations measures. His research interests also encompass comparative effectiveness research and health program impact evaluation.