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Amazon·Data Scientist·Technical Phone Screen·Senior

Senior
Apr 2026

Summary

Amazon DS interview with a deep experiment design question about validating an automated package-allocation system against a manual baseline. One question, but it was dense enough to feel like a full case.

Questions Asked (1)

Q1

Design a rigorous experiment to prove that an automated package-allocation system outperforms the manual baseline. Cover randomization strategy, interference/spillover mitigation, primary and guardrail metrics, pre-specified analysis plan, power calculations, ramp/rollback criteria, anti-gaming measures, and a fallback approach if clean randomization isn't feasible.

A/B Testing & ExperimentationProduct Analytics & MetricsSystem Design
Author's notes

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AI HintsAI Generated

Suggested Approach

Start by framing the experiment as a randomized controlled trial at the appropriate unit (e.g., package or route), then systematically address each requirement: randomization, interference, metrics, analysis plan, power, ramp/rollback, anti-gaming, and fallback. Emphasize pre-registration and guardrail metrics to ensure rigor and safety.

Pro tip: At Amazon, always tie metrics to customer experience and long-term value; propose a switchback or cluster randomization if interference is likely, and pre-register the analysis plan to avoid p-hacking.

1. Define unit and randomization

Choose the randomization unit (e.g., package, route, or time window) based on interference risk. Use stratified randomization by key covariates (e.g., package size, destination) to balance groups.

2. Mitigate interference and spillover

If interference is likely (e.g., shared resources), use cluster randomization (e.g., by fulfillment center) or switchback designs. Measure and adjust for spillover effects if present.

3. Select metrics and power analysis

Define primary metric (e.g., allocation accuracy) and guardrail metrics (e.g., delivery time, cost). Conduct power analysis to determine sample size and duration, accounting for intra-cluster correlation if applicable.

4. Pre-specify analysis and ramp plan

Pre-register the analysis plan including statistical tests, subgroup analyses, and handling of missing data. Define ramp-up stages with rollback criteria based on guardrail metrics.

5. Address anti-gaming and fallback

Implement anti-gaming measures (e.g., audit trails, anomaly detection). If clean randomization isn't feasible, propose quasi-experimental methods (e.g., difference-in-differences, propensity score matching) with sensitivity analyses.

Key Points to Mention

  • Randomization unit selection and stratification
  • Interference mitigation via cluster or switchback designs
  • Primary and guardrail metrics with clear definitions
  • Power calculations and minimum detectable effect
  • Pre-registration of analysis plan and ramp/rollback criteria
  • Anti-gaming measures and fallback quasi-experimental methods

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