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Design and Analyze A/B Test for Recommendation Widget

Last updated: Mar 29, 2026

Quick Overview

This question evaluates a candidate's skills in experimental design, randomization and exposure logic, sample-size and power calculations, metric selection and causal/statistical analysis, instrumentation and monitoring, and stakeholder communication for product experiments.

  • hard
  • Chime
  • Analytics & Experimentation
  • Data Scientist

Design and Analyze A/B Test for Recommendation Widget

Company: Chime

Role: Data Scientist

Category: Analytics & Experimentation

Difficulty: hard

Interview Round: Technical Screen

##### Scenario Designing and analyzing an online A/B test for a new product feature. ##### Question Explain end-to-end how you would set up, run and analyze an A/B test for launching a recommendation widget. What pitfalls could invalidate the experiment and how would you detect them? How would you determine sample size and choose primary metrics? Describe how you would communicate the results to stakeholders. ##### Hints Cover experiment design, randomization, power, metric definition, guardrails, debugging, and post-analysis decisions.

Quick Answer: This question evaluates a candidate's skills in experimental design, randomization and exposure logic, sample-size and power calculations, metric selection and causal/statistical analysis, instrumentation and monitoring, and stakeholder communication for product experiments.

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Chime logo
Chime
Aug 4, 2025, 10:55 AM
Data Scientist
Technical Screen
Analytics & Experimentation
69
0

Scenario

You are designing and analyzing an online A/B test for launching a new recommendation widget in a consumer-facing product (e.g., mobile and web app). The widget recommends relevant actions or products on a home/feed surface.

Task

Explain, end-to-end, how you would set up, run, and analyze an A/B test for this recommendation widget.

Requirements

  1. Experiment design and randomization
    • Define hypothesis, unit of assignment, eligibility/exposure, and rollout plan.
  2. Sample size and power
    • Determine minimum detectable effect (MDE), sample size, duration, and traffic ramp.
  3. Metrics
    • Choose a single primary metric, key secondary metrics, and guardrail metrics; define how each is computed.
  4. Execution and debugging
    • Instrumentation, logging, pre-checks (e.g., SRM), and live monitoring.
  5. Analysis
    • Statistical tests, variance reduction, handling triggered exposure vs ITT, and multiple comparisons.
  6. Pitfalls
    • List issues that could invalidate the experiment and how you would detect/mitigate them.
  7. Communication
    • How you would communicate results and a go/no-go recommendation to stakeholders.

Assume users can be exposed multiple times across sessions and platforms, and there is no cross-user network effect.

Solution

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