Calculate variance for coin flips
Last updated: September 9, 2025
Quick Overview
Given the following scenario about revenue per session, calculate the the sample size needed.
Goldman Sachs
September 9, 2025171
6
4,626 solved
Given the following scenario about revenue per session, calculate the the sample size needed.
Statistics questions at Goldman Sachs test your ability to reason quantitatively and design rigorous experiments. This Take-home Project 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
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?
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Problem Formulation
To calculate the variance of revenue per session based on coin flips, we need to define the random variable involved in the scenario. Let be the revenue per session. Assume that each session can...
Solution Approach
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