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Coinbase·Data Scientist·Technical Phone Screen·Senior

SeniorPrefer not to say
Jul 2026Remote

Summary

Interviewed for a Data Scientist role on the Identity & Trust team at Coinbase. The whole thing was essentially one long experiment design question with a lot of moving parts, and I left feeling like I'd covered maybe 70% of what they were actually looking for.

Questions Asked (1)

Q1

How would you design an A/B test to evaluate the launch of an identity verification feature with trust signals like verified badges and suspicious profile warnings? Walk through randomization, metrics, rare event measurement, network effects, bias sources, and how you'd interpret mixed results.

A/B Testing & ExperimentationProduct Analytics & MetricsProduct Strategy
Author's notes

This was basically a gauntlet.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the goal: to measure the impact of identity verification with trust signals on user trust and safety outcomes, while considering network effects and rare events. Then outline a randomized experiment design that accounts for potential biases and defines success metrics, including guardrails. Finally, discuss how to interpret results, especially when metrics move in different directions.

Pro tip: In two-sided markets like Coinbase, always consider network effects and interference between users; consider cluster randomization or switchback tests when individual randomization is not feasible. Also, for rare events, use surrogate metrics or longer horizons to ensure sufficient power.

1. Define Objectives and Hypotheses

Clarify the primary goal: increase trust and safety without harming user experience. Formulate hypotheses about how verified badges and warnings affect user behavior, such as increased trust leading to higher transaction completion or reduced fraud.

2. Design Randomization and Experiment Setup

Choose the randomization unit (user, session, or cluster) based on interference risk. For network effects, consider cluster randomization by social graph or geographic region. Ensure control and treatment groups are comparable and define exposure.

3. Select Metrics and Address Rare Events

Define primary metrics (e.g., trust score, transaction success rate) and guardrail metrics (e.g., false positives, user complaints). For rare events like fraud, use surrogate metrics (e.g., suspicious activity reports) or extend the experiment duration to accumulate enough events.

4. Identify and Mitigate Bias Sources

Consider biases such as selection bias (if randomization is flawed), novelty effects, and network effects. Use techniques like stratified randomization, pre-period matching, or switchback tests to mitigate.

5. Analyze and Interpret Mixed Results

If metrics conflict (e.g., trust increases but transaction volume drops), segment by user type or behavior. Use causal inference methods to understand trade-offs and decide whether to iterate, launch, or abandon.

Key Points to Mention

  • Randomization unit: user-level vs. cluster randomization to handle network effects
  • Rare event measurement: power analysis, surrogate metrics, or longer experiment duration
  • Bias sources: novelty effect, selection bias, interference, and how to mitigate
  • Metrics: primary (trust, safety) and guardrail (user experience, false positives)
  • Interpretation of mixed results: segment analysis, trade-off evaluation, and decision framework
  • Consideration of two-sided market dynamics and potential spillover effects

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.