Calculate variance for user retention

Last updated: March 21, 2026

Quick Overview

Given the following scenario about revenue per session, calculate the the p-value.

Oracle
Statistics & Math
Data Scientist
Oracle
March 21, 2026
Data Scientist
Take-home Project
Statistics & Math
Medium

230

13

1,329 solved


Given the following scenario about revenue per session, calculate the the p-value.

This statistics question from Oracle's Take-home Project 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
Causal inference basics
Bayesian vs frequentist inference
Confidence intervals and significance levels
Central Limit Theorem
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 assumptions does this test make, and how would you validate them?
  • What if the sample size is very small?
  • How would you explain this result to a non-technical audience?
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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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