Welcome to your interview.
The question is on your right: Set Up A/B Test Sample Size. Take a moment with it first.
Talk your thinking through with me if you like - when you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes). Discussion and graded submissions share your five interviewer interactions, so spend them well.
Describe the process of setting up an A/B test for a new UI change; how do you determine the sample size?