Calculate variance for A/B test results
Last updated: July 2, 2025
Quick Overview
Given the following scenario about revenue per session, calculate the the p-value.
Zillow
July 2, 20253
5
2,064 solved
Given the following scenario about revenue per session, calculate the the p-value.
Zillow asks this during the Technical 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
- 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
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 you discover a bug in the logging during the experiment?
- How would you handle an experiment where the control and treatment groups are different sizes?
- How would you handle seasonality in your experiment?
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Problem Setup
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Methodology
To calculate the p-value for the A/B test results, we will use a two-sample t-test for independent samples. This test is appropriate because we want to compare the means of two independent groups (con...
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