Design an A/B test for a new checkout flow
Last updated: February 7, 2026
Quick Overview
Design an experiment to test the impact of a redesigned homepage. Include sample size calculation, metrics, and analysis plan.
xAI
February 7, 202624
6
405 solved
Design an experiment to test the impact of a redesigned homepage. Include sample size calculation, metrics, and analysis plan.
This statistics question from xAI's Phone Screen 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 design a follow-up experiment based on these results?
- What if the sample size is very small?
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Browse Statistics QuestionsSample Answer
Problem Formulation
To evaluate the impact of a redesigned homepage on conversion rates during the checkout process, we will set up an A/B test.
- Hypotheses:
- Null Hypothesis (H0): The conversion rate of th...
Solution Approach
To design the A/B test, follow these steps:
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Sample Size Calculation: Use the formula for estimating sample size for comparing two proportions:
[ n = \frac{(Z_{\alpha/2} + Z_{\beta})^2 ...
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