Interpret a statistically significant lift of 2% from an experiment

Last updated: April 30, 2026

Quick Overview

An experiment shows conflicting results. What conclusions can you draw? What are the caveats?

Brex
Analytics & Experimentation
Data Scientist
Brex
April 30, 2026
Data Scientist
Take-home Project
Analytics & Experimentation
Easy

50

4

1,333 solved


An experiment shows conflicting results. What conclusions can you draw? What are the caveats?

Analytics questions at Brex evaluate your ability to define metrics, design experiments, and derive actionable insights from data. This Take-home Project question tests your end-to-end analytical thinking.

What the Interviewer Expects
  • Define clear success metrics aligned with business goals
  • Propose a basic experimental design with control and treatment groups
  • Interpret results correctly and draw reasonable conclusions
  • Identify obvious confounding variables
Key Topics to Cover
Metric definition and success criteria
Segmentation and heterogeneous effects
Simpson's paradox and ecological fallacy
Long-term vs short-term metrics
Funnel analysis and cohort analysis
Network effects and interference
How to Approach This
  1. Define success metrics carefully. A good metric is measurable, actionable, and aligned with business goals.
  2. Run experiments long enough to account for novelty effects and weekly seasonality.
  3. Use funnel analysis to identify where users drop off for maximum optimization impact.
  4. Segment results by key dimensions (platform, country, user cohort) to catch hidden patterns.
  5. Consider network effects and interference between treatment and control groups.
Possible Follow-up Questions
  • How would you handle interference between treatment and control?
  • How would you handle an experiment where the control and treatment groups are different sizes?
  • What if you discover a bug in the logging during the experiment?
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