Design an A/B test for a recommendation algorithm

Last updated: June 8, 2026

Quick Overview

Design an experiment to test the impact of new pricing tiers. Include sample size calculation, metrics, and analysis plan.

Compass
Analytics & Experimentation
Data Scientist
Compass
June 8, 2026
Data Scientist
Onsite
Analytics & Experimentation
Easy

6

5

3,511 solved


Design an experiment to test the impact of new pricing tiers. Include sample size calculation, metrics, and analysis plan.

Compass asks this during the Onsite to assess your experimentation skills. They want to see how you define success metrics, design controlled experiments, and interpret results with appropriate statistical rigor.

What the Interviewer Expects
  • Define clear success metrics aligned with business goals
  • Propose a basic experimental design with control and treatment groups
  • Interpret results correctly and draw reasonable conclusions
  • Identify obvious confounding variables
Key Topics to Cover
Metric definition and success criteria
A/B testing methodology
Guardrail metrics
Simpson's paradox and ecological fallacy
Segmentation and heterogeneous effects
Novelty and primacy effects
How to Approach This
  1. Define success metrics carefully. A good metric is measurable, actionable, and aligned with business goals.
  2. Run experiments long enough to account for novelty effects and weekly seasonality.
  3. Use funnel analysis to identify where users drop off for maximum optimization impact.
  4. Segment results by key dimensions (platform, country, user cohort) to catch hidden patterns.
  5. Consider network effects and interference between treatment and control groups.
Possible Follow-up Questions
  • What would you do if a stakeholder wants to end the experiment early because initial results look good?
  • How would you handle seasonality in your experiment?
  • What if you discover a bug in the logging during the experiment?
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