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Design A/B Test for New Amazon Recommendation Module

Last updated: Mar 29, 2026

Quick Overview

This question evaluates proficiency in online experimentation, statistical inference, metric design, and causal reasoning for a new home-page recommendation feature, covering hypothesis formulation, metric hierarchy and guardrails, sample-size/duration calculation, variance reduction, sequential testing, bias sources, and alternative causal-inference approaches. It is in the Analytics & Experimentation domain and is commonly asked because product and data teams must quantify the causal impact of UI/algorithm changes and balance engagement versus revenue trade-offs; the prompt tests both conceptual understanding of experimental principles and practical application of statistical and causal techniques.

  • hard
  • Amazon
  • Analytics & Experimentation
  • Data Scientist

Design A/B Test for New Amazon Recommendation Module

Company: Amazon

Role: Data Scientist

Category: Analytics & Experimentation

Difficulty: hard

Interview Round: Onsite

##### Scenario Amazon wants to test a brand-new product recommendation on the home page. ##### Question Design an A/B test to evaluate the new recommendation module. Define test and control, duration and required sample size. What primary metric would you track? How would you justify its business relevance? Define a p-value and explain how it is used to decide whether the experiment is successful. Describe potential sources of bias in this experiment and how you would guard against them. If you can only expose 5 % of users, how would you ensure adequate statistical power? Suppose the treatment lifts click-through-rate but reduces average order value; how would you decide whether to launch? Outline a causal inference approach (e.g., difference-in-differences or propensity matching) you could apply if randomization were impossible. ##### Hints Cover hypothesis formulation, metric hierarchy, variance reduction, sequential testing and guardrail metrics.

Quick Answer: This question evaluates proficiency in online experimentation, statistical inference, metric design, and causal reasoning for a new home-page recommendation feature, covering hypothesis formulation, metric hierarchy and guardrails, sample-size/duration calculation, variance reduction, sequential testing, bias sources, and alternative causal-inference approaches. It is in the Analytics & Experimentation domain and is commonly asked because product and data teams must quantify the causal impact of UI/algorithm changes and balance engagement versus revenue trade-offs; the prompt tests both conceptual understanding of experimental principles and practical application of statistical and causal techniques.

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Amazon logo
Amazon
Aug 4, 2025, 10:55 AM
Data Scientist
Onsite
Analytics & Experimentation
101
0

A/B Test Design: Home Page Recommendation Module

Scenario

Amazon plans to introduce a new product recommendation module on the home page and wants to evaluate its impact via online experimentation.

Task

Design an A/B test that covers:

  1. Hypotheses and experiment design (test vs. control, randomization unit, targeting, and triggering).
  2. Metric hierarchy: primary outcome, secondary metrics, and guardrails (with business justification).
  3. Sample size and duration: how to compute, with a small numeric example; include variance-reduction options.
  4. Statistical testing plan: define the p-value, how it informs decisions, and how to handle sequential looks.
  5. Biases: potential sources and how you would mitigate them.
  6. Limited exposure: if only 5% of users can be exposed, how to ensure adequate power.
  7. Trade-off decision: treatment raises click-through-rate (CTR) but lowers average order value (AOV); how to decide whether to launch.
  8. If randomization is not possible, outline a causal inference approach (e.g., difference-in-differences or propensity matching).

Include hypothesis formulation, metric hierarchy, variance reduction, sequential testing, and guardrail metrics.

Solution

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