Calculate variance for A/B test results
Last updated: August 12, 2025
Quick Overview
Given the following scenario about user conversion, calculate the the p-value.
Pinterest
Statistics & Math
Data Scientist
Data Scientist
Onsite
Statistics & Math
Easy
230
8
2,697 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 Onsite question evaluates your understanding of statistical inference and its application to business decisions.
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
Hypothesis testing (H0, H1, p-values)
Central Limit Theorem
Multiple testing correction (Bonferroni, FDR)
Probability distributions
Bayesian vs frequentist inference
Power analysis and sample size calculation
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 assumptions does this test make, and how would you validate them?
- How would you handle multiple comparisons?
- What alternative statistical method could you use here?
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Problem formulation
To analyze the user conversion data from an A/B test at Pinterest, we set up our hypotheses:
- Null Hypothesis (H0): There is no difference in conversion rates between the control group (A) and t...
Solution approach
To calculate the p-value, we will:
- Compute the sample proportions and .
- Calculate the pooled conversion rate using the formula: [ \hat{p} = \f...
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