Final answer:
In an internal review of a stroke patient, the process used is Root cause analysis, which helps identify the fundamental reasons for a problem to prevent recurrence.
Step-by-step explanation:
The performance improvement process being used in an in-depth internal review of a stroke patient found unconscious on the floor is Root cause analysis. Root cause analysis is a systematic process for identifying root causes of problems or events and an approach for responding to them. This process is critical in healthcare to prevent future incidents. In contrast, PDSA (Plan, Do, Study, Act) is a model for continuous improvement, Six Sigma is a set of techniques for process improvement, and DMAIC (Define, Measure, Analyze, Improve, Control) is a data-driven quality strategy for improving processes.