You work on a ride-sharing marketplace with a new ad product that promotes certain merchant or driver-partner offers inside the app. Early results show higher clicks and conversions on promoted placements, but you are concerned the ads may be cannibalizing behavior that would have happened anyway rather than creating true incremental value.
What would you look at to determine whether the ad product is generating incremental conversions instead of simply shifting existing demand across placements or time? How would you design and interpret an experiment to answer that question?