Lean is a methodology focused on eliminating waste and improving efficiency. Among its concepts, the one associated with rapid improvement is most relevant to the question.

Option A (Kaizen): This is the correct answer. Kaizen, meaning “continuous improvement” in Japanese, involves rapid, incremental improvements through focused events (e.g., Kaizen blitz) where teams address specific process issues quickly. NAHQ CPHQ study materials identify Kaizen as a Lean tool for achieving swift, collaborative improvements.

Option B (Six Sigma): Six Sigma focuses on reducing variation and improving quality through data-driven methods (e.g., DMAIC), but it is typically a longer, more analytical process, not rapid improvement.

Option C (Poka-yoke): Poka-yoke refers to mistake-proofing techniques to prevent errors (e.g., color-coded labels). While effective, it is not specifically about rapid improvement but error prevention.

Option D (Kanban): Kanban is a Lean tool for managing workflow and inventory (e.g., visual boards). It supports efficiency but is not centered on rapid improvement events.