Design an A/B test for a search ranking change
Last updated: March 8, 2026
Quick Overview
Design an experiment to test the impact of a redesigned homepage. Include sample size calculation, metrics, and analysis plan.
Square/Block
March 8, 2026203
4
2,016 solved
Design an experiment to test the impact of a redesigned homepage. Include sample size calculation, metrics, and analysis plan.
Square/Block asks this during the Phone Screen 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
- Design complex experimentation strategies for tricky scenarios
- Handle multi-armed bandits, switchback experiments, and quasi-experiments
- Address long-term effects vs short-term metrics
- Propose causal inference methods when randomization is not possible
- Build a measurement framework that connects metrics to business value
- Discuss organizational experimentation culture and maturity
Key Topics to Cover
How to Approach This
- Define success metrics carefully. A good metric is measurable, actionable, and aligned with business goals.
- Run experiments long enough to account for novelty effects and weekly seasonality.
- Use funnel analysis to identify where users drop off for maximum optimization impact.
- Segment results by key dimensions (platform, country, user cohort) to catch hidden patterns.
- Consider network effects and interference between treatment and control groups.
Possible Follow-up Questions
- What if the experiment shows a positive short-term effect but you suspect a negative long-term impact?
- How would you handle interference between treatment and control?
- What if you discover a bug in the logging during the experiment?
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Browse Analytics QuestionsSample Answer
Problem Setup
The analytical question is: "What is the impact of the redesigned homepage on user engagement and conversion rates?" To answer this, we need data on user interactions on both the old and new homepage ...
Methodology
We will implement a classic A/B test with a control group (old homepage) and a treatment group (new homepage). The sample size calculation is crucial to ensure statistical power. Using the formula for...
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