ABSTRACT
This article explores the application of open science practices, focusing on the challenges, barriers, and lessons learned from preregistering outcomes and analytic protocols in impact evaluation. Using the Health Profession Opportunity Grants (HPOG) Program Impact Study as a case study, we illustrate the balance between pre-specifying research plans and maintaining flexibility to adapt to unexpected findings. We discuss how preregistration can enhance transparency, credibility, and the overall quality of evidence, as well as practical considerations for future evaluations. Our insights aim to guide evaluators in applying open science principles to improve the rigor and integrity of impact evaluations.