Experiments and clinical trials are the "gold standard’’ for evidence in economics and medicine. It is straightforward to analyze them to determine the average impact of a treatment. However, even if a treatment helps patients on average, it is much more difficult to determine if it will help all patients equally. Using methods from economics, I re-analyze data from experiments and clinical trials with the goal of personalizing recommendations. As an economist, I take into account not only whether the recommendations are sound, but also who will follow them.