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Uber·Data Scientist·Technical Phone Screen·Senior

Senior
Jul 2026

Summary

Uber data scientist interview with a pretty brutal causal inference question about a messy real-world A/B test. The kind of problem where you think you know the framework and then realize halfway through that there are like three simultaneous complications to untangle.

Questions Asked (1)

Q1

You ran an A/B test on surge recommendations sent to drivers, but 30% of treated drivers ignored the suggestion and surge in one zone spills over into neighboring zones. How would you estimate the causal effect on completed trips, and what analysis plan would you use to handle both the noncompliance and the interference?

A/B Testing & ExperimentationProduct Analytics & MetricsTechnical Trade-offs
Author's notes

This one took me a minute to even parse.

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AI HintsAI Generated

Suggested Approach

First, define the causal estimand as the effect of the surge recommendation on completed trips, accounting for both noncompliance and interference. Then, propose a two-stage approach: use instrumental variables (IV) to handle noncompliance and a design-based or model-based method to address interference, such as cluster randomization or spatial regression discontinuity. Finally, outline sensitivity analyses to test assumptions.

Pro tip: Emphasize that in ride-hailing, interference is often the norm, so proactively suggest designs like switchback or geo-based randomization, and clarify that IV estimates a local average treatment effect (LATE) for compliers.

1. Define the causal estimand and assumptions

Clarify that the goal is the effect of the surge recommendation on completed trips, and state assumptions like exclusion restriction for IV and no interference between clusters.

2. Address noncompliance with instrumental variables

Use random assignment as an instrument for actual surge acceptance, estimating the LATE via two-stage least squares or Wald estimator.

3. Handle interference via design or modeling

If interference is present, consider cluster randomization (e.g., by zone) or spatial models that account for spillovers, such as a spatial autoregressive model or difference-in-differences with spillover terms.

4. Estimate the causal effect

Combine methods: e.g., use IV within a cluster-randomized design, or apply a spatial IV approach. Estimate the effect on completed trips, possibly using a two-stage least squares with spatial lags.

5. Conduct sensitivity and robustness checks

Test sensitivity to interference assumptions, check for weak instruments, and validate with placebo tests or alternative specifications.

Key Points to Mention

  • Instrumental variables (IV) to handle noncompliance, estimating LATE
  • Interference/spillover effects and the need for cluster randomization or spatial methods
  • Potential outcomes framework and causal estimands (ATE, LATE)
  • Spatial regression discontinuity or difference-in-differences with spillovers
  • Sensitivity analysis for assumptions like exclusion restriction and no interference
  • Practical considerations: switchback designs, geo-based randomization, and network effects

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