Calculate probability for click-through rates

Last updated: October 5, 2025

Quick Overview

Given the following scenario about revenue per session, calculate the the sample size needed.

Booking.com
Statistics & Math
Data Scientist
Booking.com
October 5, 2025
Data Scientist
Take-home Project
Statistics & Math
Medium

88

4

840 solved


Given the following scenario about revenue per session, calculate the the sample size needed.

Statistics questions at Booking.com 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
  • 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
Conditional probability and Bayes theorem
Multiple testing correction (Bonferroni, FDR)
Central Limit Theorem
Regression analysis
Power analysis and sample size calculation
Hypothesis testing (H0, H1, p-values)
How to Approach This
  1. Define your hypotheses (H0 and H1) clearly before performing any test.
  2. Calculate required sample size BEFORE running an experiment, using power analysis.
  3. Remember the Central Limit Theorem: sample means become approximately normal with large n.
  4. Watch for Simpson's paradox. Always segment data by key dimensions.
  5. Distinguish between statistical significance and practical significance.
Possible Follow-up Questions
  • How would you design a follow-up experiment based on these results?
  • What assumptions does this test make, and how would you validate them?
  • What if the sample size is very small?
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Sample Answer
Setting Up the Problem

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Solution Approach

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