Your question is Homepage Banner A/B Test Design. Take a moment with it on the right.
Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).
You work on a product team that wants to add a new promotional banner to the homepage. The banner could increase clicks and downstream conversion, but it might also distract users from their main tasks or create a noisier homepage experience.
How would you design an A/B test for this new homepage promotional banner? Walk through the hypothesis, success metrics, sample size, experiment setup, and how you would decide whether to ship.