Calculate variance for coin flips
Last updated: September 11, 2025
Quick Overview
Given the following scenario about revenue per session, calculate the the sample size needed.
Grubhub
Statistics & Math
Data Scientist
Grubhub
September 11, 2025Data Scientist
Onsite
Statistics & Math
Medium
46
10
4,397 solved
Given the following scenario about revenue per session, calculate the the sample size needed.
Statistics questions at Grubhub test your ability to reason quantitatively and design rigorous experiments. This Onsite question evaluates your understanding of statistical inference and its application to business decisions.
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
Multiple testing correction (Bonferroni, FDR)
Probability distributions
Regression analysis
Confidence intervals and significance levels
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?
- How would you handle multiple comparisons?
- How would you design a follow-up experiment based on these results?
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Browse Statistics QuestionsSample Answer
Problem Formulation
To determine the sample size needed for estimating the revenue per session at Grubhub based on coin flips, we first need to define the parameters of our study. Let:
- be the probability of suc...
Solution Approach
- Determine parameters: Assume we want to estimate the probability of revenue exceeding a certain threshold, with (assuming no prior data).
- Set desired margin of error: Let’s...
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