Design an A/B test for a search ranking change

Last updated: July 18, 2025

Quick Overview

Design an experiment to test the impact of a redesigned homepage. Include sample size calculation, metrics, and analysis plan.

Scale AI
Analytics & Experimentation
Product Manager
Scale AI
July 18, 2025
Product Manager
Take-home Project
Analytics & Experimentation
Easy

25

1

970 solved


Design an experiment to test the impact of a redesigned homepage. Include sample size calculation, metrics, and analysis plan.

Analytics questions at Scale AI evaluate your ability to define metrics, design experiments, and derive actionable insights from data. This Take-home Project question tests your end-to-end analytical thinking.

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
A/B testing methodology
Guardrail metrics
Segmentation and heterogeneous effects
Simpson's paradox and ecological fallacy
Long-term vs short-term metrics
Funnel analysis and cohort analysis
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
  • How would you handle an experiment where the control and treatment groups are different sizes?
  • What if the experiment shows a positive short-term effect but you suspect a negative long-term impact?
  • How would you handle seasonality in your experiment?
  • What if you discover a bug in the logging during the experiment?
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