Design an evaluation framework for ads ranking.

Focus on defining the key metrics that will determine the effectiveness of ad ranking, such as click-through rates, conversion rates, and user engagement. Consider how to balance relevance and revenue when ranking ads, and think about the user experience—how ads can be personalized without being intrusive. Discuss the importance of A/B testing and how you would implement it to validate your framework. Finally, address potential biases in ad ranking and how to mitigate them to ensure fairness and transparency.