Measure a channel's incrementality without user tracking
Causal inferenceHardProblem. Post-IDFA you can't reliably track users, but you need the causal incremental effect of a paid channel. Design a geo incrementality experiment. How do you run and read it?
Before you reveal: say your answer out loud, as if you were in the real interview — get your reasoning across clearly first. There is no single correct answer: reading what the interviewer is really after and defending your own thinking is what makes an answer strong.