Design an A/B test for a search ranking change
Last updated: October 13, 2025
Quick Overview
Design an experiment to test the impact of a redesigned homepage. Include sample size calculation, metrics, and analysis plan.
HubSpot
October 13, 2025139
5
4,341 solved
Design an experiment to test the impact of a redesigned homepage. Include sample size calculation, metrics, and analysis plan.
Statistics questions at HubSpot test your ability to reason quantitatively and design rigorous experiments. This Technical Screen question evaluates your understanding of statistical inference and its application to business decisions.
What the Interviewer Expects
- Set up the problem formally with proper notation
- Apply the correct statistical test with clear justification
- Interpret results with appropriate caveats and confidence levels
- Discuss practical significance vs statistical significance
- Identify potential confounders and how to address them
Key Topics to Cover
How to Approach This
- Define your hypotheses (H0 and H1) clearly before performing any test.
- Calculate required sample size BEFORE running an experiment, using power analysis.
- Remember the Central Limit Theorem: sample means become approximately normal with large n.
- Watch for Simpson's paradox. Always segment data by key dimensions.
- Distinguish between statistical significance and practical significance.
Possible Follow-up Questions
- How would you design a follow-up experiment based on these results?
- What if the sample size is very small?
- How would you handle multiple comparisons?
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Browse Statistics QuestionsSample Answer
Problem Formulation
To assess the impact of a redesigned homepage on user engagement, we will conduct an A/B test. This involves splitting the incoming traffic into two groups: Group A (control) will see the current home...
Solution Approach
- Determine the Metrics: Choose a primary metric for user engagement (e.g., CTR).
- Set the Significance Level: Commonly, we use a significance level .
- **Effect Size Es...
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