Should WhatsApp launch group calls?
Company: Meta
Role: Data Scientist
Category: Analytics & Experimentation
Difficulty: medium
Interview Round: Technical Screen
WhatsApp currently supports only one-to-one calling and is considering launching group calling for personal users. The product goal is to increase engagement without materially hurting call quality, reliability, or user trust.
How would you evaluate whether launching group calling is a good idea? In your answer:
1. Define the user problem, target segment, and key product hypotheses.
2. Propose pre-launch sizing analyses and success metrics that could be computed from communication data such as call counts, call minutes, distinct contacts, and user activity.
3. Design an A/B test for the launch. Specify the experimental unit, primary metric, secondary metrics, and guardrails.
4. Explain why a metric such as `percentage of users who made a group call` is not a valid primary success metric for the experiment, even though it may still be useful as a treatment-only diagnostic.
5. Because communication products have strong network effects, discuss whether you would use user-level randomization or cluster randomization, and explain the main drawbacks of cluster randomization.
Assume you have standard communication logs for users, one-to-one calls, and post-launch group-call events in treatment.
Quick Answer: This question evaluates a data scientist's skills in experiment design, product analytics, metric definition, causal inference, and managing network effects for a messaging app feature, and is categorized under Analytics & Experimentation.