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Amazon·Data Scientist·Technical Phone Screen·Senior

Senior
Jul 2026

Summary

Amazon DS interview with a meaty causal inference case about a customer compensation pilot. The question had a lot of moving parts and felt more like a take-home problem compressed into a conversation.

Questions Asked (2)

Q1

Some regions piloted a program where customers affected by lost or damaged shipments receive a gift card instead of just a refund or replacement. How would you evaluate whether this program worked?

A/B Testing & ExperimentationProduct Analytics & MetricsRoot Cause Analysis
Author's notes

This one sprawled fast.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the program's goal (e.g., improving customer satisfaction, retention, or reducing costs) and then define success metrics across customer, operational, and financial dimensions. Propose a rigorous evaluation design, such as a randomized controlled trial or quasi-experimental methods, and outline how to measure and interpret the impact.

Pro tip: Emphasize the importance of measuring long-term customer lifetime value (CLV) and retention, not just immediate satisfaction, because gift cards may drive repeat purchases but could also attract deal-seeking behavior. Also, consider the cost-effectiveness compared to traditional resolutions.

1. Define Objectives and Hypotheses

Clarify what the program aims to achieve (e.g., increase customer satisfaction, retention, or reduce costs) and formulate testable hypotheses. For example, H1: Gift cards increase repeat purchase rate compared to refunds.

2. Select Metrics and Design

Choose primary and secondary metrics (e.g., CSAT, repeat purchase rate, CLV, resolution cost) and design an experiment (e.g., randomized controlled trial) or quasi-experimental study if randomization isn't possible.

3. Collect and Analyze Data

Gather data on treatment and control groups, ensuring comparability. Use statistical methods (e.g., t-tests, regression, difference-in-differences) to estimate the program's causal impact, checking for significance and effect size.

4. Evaluate Business Impact and Trade-offs

Assess whether the program improved key outcomes and calculate ROI, considering both short-term costs and long-term benefits. Analyze heterogeneous effects across customer segments.

5. Recommend and Iterate

Based on findings, recommend scaling, modifying, or discontinuing the program. Suggest further experiments to optimize gift card value or targeting.

Key Points to Mention

  • Define clear success metrics aligned with business goals (e.g., customer satisfaction, retention, cost per resolution).
  • Use a randomized controlled trial (A/B test) to establish causality, with proper randomization and sample size.
  • Consider long-term metrics like customer lifetime value (CLV) and repeat purchase behavior, not just immediate satisfaction.
  • Account for potential confounders and selection bias; use quasi-experimental methods if randomization is not feasible.
  • Analyze cost-effectiveness: compare the cost of gift cards vs. refunds/replacements and the incremental revenue from repeat purchases.
  • Segment analysis to understand heterogeneous treatment effects (e.g., by customer tenure, order value, region).

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

Q2

If you could redesign this as a randomized experiment from scratch, how would you set it up?

A/B Testing & ExperimentationProduct Strategy
Author's notes

Follow-up that came right after.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the current setup and the causal question you want to answer, then outline a randomized experiment design that isolates the effect of the key change. Structure your answer around hypothesis, unit of randomization, metrics, and analysis plan, while addressing practical constraints like interference and sample size.

Pro tip: Acknowledge that a perfect randomized experiment may not be feasible in practice, and propose a pragmatic design (e.g., switchback or cluster randomization) that balances internal validity with operational constraints—this shows you understand real-world experimentation at Amazon scale.

1. Define the causal question and hypothesis

Clearly state what change you want to test and the expected impact, ensuring the hypothesis is specific, measurable, and tied to a business metric.

2. Choose randomization unit and assignment

Decide whether to randomize at the user, session, or cluster level, and explain how you would assign treatments to avoid bias and contamination.

3. Select primary and guardrail metrics

Identify the key success metric (e.g., conversion, revenue) and guardrail metrics (e.g., latency, customer satisfaction) to monitor unintended consequences.

4. Determine sample size and duration

Perform power analysis to calculate required sample size and experiment duration, accounting for expected effect size, variance, and traffic.

5. Plan analysis and address pitfalls

Outline statistical tests, handling of multiple comparisons, and strategies for common issues like network effects, novelty effects, and non-compliance.

Key Points to Mention

  • Randomization unit (user, session, cluster) and its implications for interference and generalizability
  • Primary metric (e.g., conversion rate) and guardrail metrics (e.g., page load time, return rate)
  • Power analysis: sample size, minimum detectable effect, significance level, and power
  • Potential biases: novelty effect, primacy effect, selection bias, and how to mitigate them
  • Analysis methods: t-test, regression adjustment, sequential testing, or Bayesian approaches
  • Practical constraints: traffic volume, ethical considerations, and feasibility of full randomization

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