Calculate expected value for user retention

Last updated: February 2, 2026

Quick Overview

Given the following scenario about user conversion, calculate the the p-value.

Pinterest
Statistics & Math
Data Scientist
Pinterest
February 2, 2026
Data Scientist
Technical Screen
Statistics & Math
Hard

12

6

1,076 solved


Given the following scenario about user conversion, calculate the the p-value.

Statistics questions at Pinterest 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
  • 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
Central Limit Theorem
Conditional probability and Bayes theorem
Confidence intervals and significance levels
Probability distributions
Bayesian vs frequentist inference
How to Approach This
  1. Define your hypotheses (H0 and H1) clearly before performing any test.
  2. Calculate required sample size BEFORE running an experiment, using power analysis.
  3. Remember the Central Limit Theorem: sample means become approximately normal with large n.
  4. Watch for Simpson's paradox. Always segment data by key dimensions.
  5. Distinguish between statistical significance and practical significance.
Possible Follow-up Questions
  • What if the sample size is very small?
  • How would you explain this result to a non-technical audience?
  • What alternative statistical method could you use here?
  • What assumptions does this test make, and how would you validate them?
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Sample Answer
Setting Up the Problem

Start by formalizing the problem: 1. **Define the hypotheses**: H0 (null hypothesis) and H1 (alternative). Be precise about what you're testing. 2. ...

Solution Approach

**Compute the test statistic**: Apply the appropriate formula using the sample data. **Find the p-value**: The probability of observing a result this...


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