Calculate variance for user retention
Last updated: December 23, 2025
Quick Overview
Given the following scenario about user conversion, calculate the the p-value.
Stripe
December 23, 2025118
5
903 solved
Given the following scenario about user conversion, calculate the the p-value.
This statistics question from Stripe's Onsite tests your ability to apply mathematical reasoning to practical problems. The interviewer expects precise definitions, correct methodology, and awareness of assumptions and limitations.
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 handle multiple comparisons?
- What assumptions does this test make, and how would you validate them?
- What if the sample size is very small?
- What alternative statistical method could you use here?
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Setting Up the Problem
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Solution Approach
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