Interpret a statistically significant lift of 2% from an experiment

Last updated: December 16, 2025

Quick Overview

An experiment shows a 3% lift with p=0.08. What conclusions can you draw? What are the caveats?

DE Shaw
Analytics & Experimentation
Data Scientist
DE Shaw
December 16, 2025
Data Scientist
Technical Screen
Analytics & Experimentation
Medium

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An experiment shows a 3% lift with p=0.08. What conclusions can you draw? What are the caveats?

DE Shaw asks this during the Technical Screen to assess your experimentation skills. They want to see how you define success metrics, design controlled experiments, and interpret results with appropriate statistical rigor.

What the Interviewer Expects
  • Design a rigorous experiment with proper randomization and sample size calculation
  • Define primary and guardrail metrics with clear rationale
  • Address novelty effects, network effects, and interference
  • Segment results appropriately and identify heterogeneous treatment effects
  • Propose follow-up analyses when results are ambiguous
Key Topics to Cover
Simpson's paradox and ecological fallacy
Funnel analysis and cohort analysis
Novelty and primacy effects
Sample size and power calculation
Long-term vs short-term metrics
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
  • What if you discover a bug in the logging during the experiment?
  • How would you handle an experiment where the control and treatment groups are different sizes?
  • How would you handle seasonality in your experiment?
  • How would you handle interference between treatment and control?
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