Kanban is the signaling system used to communicate the need for units or components in a pull environment. In Lean Six Sigma, kanban controls the flow of material by authorizing production or movement only when downstream demand requires it. The signal may take the form of a card, bin, visual marker, electronic trigger, or other indicator, but the purpose is the same: to tell the upstream process that more items are needed. This helps prevent overproduction, reduce inventory, improve flow, and synchronize replenishment with actual consumption. Changeover refers to switching from one setup or product to another. Poka-yoke is mistake-proofing. An andon cord is a visual or audible alert used to signal abnormalities or call for help, not to request replenishment of parts in a pull system. In Six Sigma improvement work, understanding kanban is important because it links process design with demand-based control and waste reduction. Therefore, the correct answer is Kanban, because it is the specific system that uses signals to communicate the need for units or components within a pull-based process.

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