Explain how you would use A/B testing to improve customer retention.

Example answer

I would define a specific change and retention endpoint before launch. For example, test a revised onboarding flow among new eligible users and measure whether each user returns during days 28 through 34 after assignment. This makes the cohort, observation window and denominator explicit. Daily active users or satisfaction scores can be useful diagnostics, but they are not interchangeable with this retention measure.

I would randomize users consistently, preserve assignment across sessions and analyze the eligible assigned cohort under the pre-specified approach. I would check exposure and logging quality without removing users merely because they did not engage with the new flow. That behavior may itself be affected by treatment.

I would plan sample size, enrollment length and analysis in advance, then allow every included cohort to complete its retention window. Recent users with incomplete follow-up are not automatically churned users. If a time-to-event analysis is chosen instead, its event and censoring rules need to be defined explicitly.

I would report the difference in retention with uncertainty and examine guardrails such as support burden, cancellation and harmful notifications. I would not keep extending a fixed-horizon test until it becomes significant. A positive short-term outcome would justify a decision only within its scope; longer follow-up may be needed to see whether the benefit persists.

Assessment: A strong answer defines who is counted and when, handles incomplete follow-up, and separates the randomized effect estimate from speculative explanations of why it occurred.