This research is funded by the World Bank Development Impact Evaluation (DIME). The credibility revolution triggered a paradigm shift in economics. This research examines its causal effects on bureaucrats in a “mastering metrics” training program. We separate the demand for mastering metrics from its impact with a simplified Becker DegrootMarshak mechanism. Policymakers could choose a high or low probability for randomly receiving a mastering metrics book or a self-help placebo book. After receiving the book, policy-makers will participate in an intense training workshop that included watching lecture videos made by the authors of the book, summarizing each chapter, discussing, and applying the book’s concepts in their policymaking. (AEA RCT Registry)