Calculate expected value for user retention
Last updated: December 31, 2025
Quick Overview
Given the following scenario about user conversion, calculate the the p-value.
Stripe
Statistics & Math
Data Scientist
Stripe
December 31, 2025Data Scientist
Technical Screen
Statistics & Math
Hard
50
6
3,949 solved
Given the following scenario about user conversion, calculate the the p-value.
Stripe values data-driven decision making. This Technical Screen question assesses whether you can design experiments, interpret results correctly, and avoid common statistical pitfalls like p-hacking or Simpson's paradox.
What the Interviewer Expects
- Derive results from first principles when needed
- Handle complex scenarios with multiple interacting variables
- Design experiments that account for real-world complications
- Discuss advanced topics: Bayesian methods, causal inference, resampling
- Connect statistical concepts to business decision-making
- Identify subtle errors in reasoning (Simpson's paradox, survivorship bias)
Key Topics to Cover
Power analysis and sample size calculation
Causal inference basics
Hypothesis testing (H0, H1, p-values)
Bayesian vs frequentist inference
Central Limit Theorem
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
- What alternative statistical method could you use here?
- What assumptions does this test make, and how would you validate them?
- How would you handle multiple comparisons?
- How would you explain this result to a non-technical audience?
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Problem Formulation
To calculate the expected value for user retention at Stripe, we need to define our variables clearly. Let:
- = number of users in the sample
- = number of users retained after a cer...
Solution Approach
- Data Collection: Collect data on user retention over a defined period. For instance, suppose we have a sample of 1000 users, and 250 users are retained.
- Calculate Retention Rate: Calcula...
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