Calculate conditional probability for A/B test results

Last updated: September 1, 2025

Quick Overview

Given the following scenario about user conversion, calculate the the p-value.

Uber
Statistics & Math
Data Scientist
Uber
September 1, 2025
Data Scientist
Technical Screen
Statistics & Math
Easy

427

5

4,966 solved


Given the following scenario about user conversion, calculate the the p-value.

This statistics question from Uber's Technical 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
Probability distributions
Conditional probability and Bayes theorem
Causal inference basics
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
  • What alternative statistical method could you use here?
  • How would you design a follow-up experiment based on these results?
  • How would you explain this result to a non-technical audience?
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Sample Answer
Problem Formulation

We are tasked with calculating the p-value for an A/B test conducted by Uber to evaluate user conversion rates. Let's define our variables:

  • Let AA be the event that a user converts after seein...
Solution Approach

To calculate the p-value, we will follow these steps:

  1. Collect the sample sizes and conversion counts for both groups:
    • Let nAn_A be the number of users in group A, and kAk_A be the numb...

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