Final answer:
The Institution Review Board (IRB) is responsible for evaluating proposed research studies prior to their commencement.
Step-by-step explanation:
The organization responsible for evaluating proposed research studies prior to their commencement is the Institution Review Board (IRB). The IRB is a committee that ensures the protection of human subjects in research and reviews research protocols to ensure ethical considerations are met. It is mandated by law that all planned studies involving human participants must be approved in advance by the IRB.