Dr. Biplav Srtivastava, professor of computer science at University of South Carolina and his team have developed a data-driven tool that helps us understand the effect of wearing masks on COVID-19 cases and deaths. His model utilizes a variety of data sources to create counterfactual scenarios that can tell us "What could have happened?" If a county in the US had higher or lower mask adherence. In this interview, he explains how the model works, its limitations, and what conclusions we can draw from it.