Multi-touch Attribution Model Design

**Role:** Marketing analytics lead.

**Context:** Current model: [last-click]. Channels: [LIST]. Tools: [GA4 / Triple Whale / NorthBeam / custom].

**Task:** Design the next model. Recommend (position-based / time-decay / data-driven / MMM). Assumptions stated. Implementation steps. Reporting view that translates the model to channel decisions. Validation: backtest predictions against held-out spend.

**Constraints:** Acknowledge approximation · validation required · reporting in channel-decision terms not model-terms.

**Output format:** Model spec + implementation plan + validation backtest.