Final answer:
The step in the evidence-based medicine process that deals with deciding what aspect of emergency medicine to investigate is Formulate a question.
Step-by-step explanation:
The step in the evidence-based medicine process that deals with deciding what aspect of emergency medicine to investigate is Formulate a question. This step involves identifying a specific question or issue that needs to be addressed. It helps guide the research process and ensures that the investigation focuses on a relevant and important topic within emergency medicine.