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Design A/B test for AI chat box

RedditData Scientist · Onsite
EasyData ScientistOnsiteAnalytics & Experimentation

Last updated

This question tests the ability to define metrics, design an A/B testing framework, and account for potential biases when deploying a new AI-powered chat feature.

Scenario

Reddit is testing a new AI-powered chat assistant that proactively suggests community-relevant topics to users in subreddit threads. The goal is to increase user engagement and foster deeper community interactions.

Task

Design an A/B test to evaluate the effectiveness of this AI chat assistant. Your response should address:

  1. Metric Definition: Define a primary metric to measure success and at least two guardrail metrics to ensure the feature doesn't negatively impact the platform.
  2. Experiment Design: Describe the randomization strategy and how you would determine the sample size.
  3. Evaluation: Explain how you would interpret the results, considering potential novelty effects or interaction effects.

Constraints

  • Assume you have access to standard event-logging infrastructure.
  • Consider that Reddit users are highly sensitive to changes that feel like "spam" or "corporate interference."
  • The AI assistant consumes compute resources, so latency and cost-per-impression are relevant concerns.

Hints

Hint 1

Focus on metrics that balance immediate engagement, such as message volume, against long-term community health.

Hint 2

Consider if randomization should occur at the user level or the subreddit level to avoid interference between groups.

Hint 3

Think about how the 'novelty effect' might inflate engagement initially and how you would distinguish that from sustained utility.

Follow-up questions

  • How would you handle a scenario where the AI assistant increases total messages but decreases the average sentiment or 'helpfulness' score of threads?
  • If the AI assistant is computationally expensive, how would you incorporate the cost-per-inference into your final decision-making framework?
  • How would you account for users who interact with the AI assistant across multiple devices, and what does this mean for your experiment's unit of randomization?