Explain multiple testing correction with an example

Last updated: March 4, 2026

Quick Overview

Explain multiple testing correction in simple terms and provide a concrete example.

Reddit
Analytics & Experimentation
Data Scientist
Reddit
March 4, 2026
Data Scientist
Onsite
Analytics & Experimentation
Hard

60

4

1,655 solved


Explain multiple testing correction in simple terms and provide a concrete example.

This analytics question from Reddit's Onsite tests your ability to think critically about data. The interviewer expects you to consider confounding variables, selection bias, and the difference between correlation and causation.

What the Interviewer Expects
  • Design complex experimentation strategies for tricky scenarios
  • Handle multi-armed bandits, switchback experiments, and quasi-experiments
  • Address long-term effects vs short-term metrics
  • Propose causal inference methods when randomization is not possible
  • Build a measurement framework that connects metrics to business value
  • Discuss organizational experimentation culture and maturity
Key Topics to Cover
Sample size and power calculation
Simpson's paradox and ecological fallacy
Funnel analysis and cohort analysis
Guardrail metrics
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
  • What if you discover a bug in the logging during the experiment?
  • How would you handle interference between treatment and control?
  • What if the experiment shows a positive short-term effect but you suspect a negative long-term impact?
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