How big should the holdout from all marketing messages be?
Power & sample sizeMediumProblem. Marketing wants to keep a permanent holdout of travelers who receive no marketing emails or push messages, to measure the total value of messaging powered by the customer data platform. They'd like it as small as possible, say 0.5%, because held-out travelers book less. There are 50 million eligible travelers. How big should it be?
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.