Calculate conditional probability for user retention
Last updated: July 23, 2025
Quick Overview
Given the following scenario about revenue per session, calculate the the sample size needed.
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Given the following scenario about revenue per session, calculate the the sample size needed.
This statistics question from Reddit'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
- State the correct formula or theorem with clear definitions
- Apply the concept to the given scenario step by step
- Interpret the result in plain language
- Identify assumptions and when they might be violated
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
- What alternative statistical method could you use here?
- What assumptions does this test make, and how would you validate them?
- How would you explain this result to a non-technical audience?
- What if the sample size is very small?
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Browse Statistics QuestionsSample Answer
Problem formulation
To calculate the sample size needed for assessing user retention on Reddit based on revenue per session, we will utilize the concepts of conditional probability and power analysis. We need to define: ...
Solution approach
To calculate the sample size, we will follow these steps:
- Estimate the Proportion: Determine an estimate of the proportion of users that return, , based on historical data.
- **Specify...
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