Your question is Fraud Rule Test Without Good-User Harm. 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 an operations team that is considering a new fraud rule for a marketplace. The rule is meant to reduce fraudulent losses, but there is concern it may also block good users and hurt legitimate activity.
How would you measure whether the new fraud rule is actually reducing losses without blocking good users? Walk through how you would structure the experiment and what evidence you would need before deciding to ship.