Design an A/B test for a pricing model

Last updated: November 6, 2025

Quick Overview

Design an experiment to test the impact of new pricing tiers. Include sample size calculation, metrics, and analysis plan.

Reddit
Statistics & Math
Data Scientist
Reddit
November 6, 2025
Data Scientist
Technical Screen
Statistics & Math
Medium

3

5

2,797 solved


Design an experiment to test the impact of new pricing tiers. Include sample size calculation, metrics, and analysis plan.

Reddit values data-driven decision making. This Technical Screen question assesses whether you can design experiments, interpret results correctly, and avoid common statistical pitfalls like p-hacking or Simpson's paradox.

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
Hypothesis testing (H0, H1, p-values)
Causal inference basics
Confidence intervals and significance levels
Central Limit Theorem
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 handle multiple comparisons?
  • What assumptions does this test make, and how would you validate them?
  • What alternative statistical method could you use here?
  • What if the sample size is very small?
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Sample Answer
Problem Formulation

To design an A/B test for Reddit's new pricing tiers, we need to define our null and alternative hypotheses. Let:

  • H0 (Null Hypothesis): There is no difference in the conversion rate of users be...
Solution Approach
  1. Determine Sample Size: We will use the formula for sample size calculation in A/B testing:

    n=(Zα/2+Zβ)2(p1(1p1)+p2(1p2))(p1p2)2n = \frac{(Z_{\alpha/2} + Z_{\beta})^2 \cdot (p_1(1-p_1) + p_2(1-p_2))}{(p_1 - p_2)^2} ...


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