What is my minimum detectable effect for typical traffic levels?
Muhammed Tüfekyapan
Founder & CEO
TL;DR - Quick Answer
Complete Expert Analysis
What Is My Minimum Detectable Effect for Typical Traffic Levels?
Minimum Detectable Effect (MDE) is the smallest conversion rate improvement your test can reliably detect given your traffic volume. If your MDE is 15% but your actual improvement is 8%, you'll falsely conclude "no winner found" and miss a real gain. Understanding your MDE before running tests prevents you from making the wrong decisions from inconclusive data.
MDE by Traffic Level and Confidence Requirements
| Monthly Sessions | Test Duration | MDE (95% confidence) | Practical Impact |
|---|---|---|---|
| 1,000 | 8-12 weeks | ~30%+ lift detectable | Only big changes detectable |
| 3,000 | 4-6 weeks | ~20% lift detectable | Moderate improvements only |
| 10,000 | 2-3 weeks | ~12% lift detectable | Useful range |
| 30,000 | 1-2 weeks | ~7% lift detectable | Good sensitivity |
| 100,000+ | Days | ~3-5% lift detectable | Excellent sensitivity |
What This Means for Small-Traffic Stores
If your monthly sessions are under 5,000, traditional A/B testing has limited applicability. Focus instead on:
- -Big, bold tests only: Test changes that could realistically produce 25%+ lifts (complete page redesigns, major offer changes)
- -Qualitative research: User interviews, session recordings, and heatmaps give richer insights than underpowered A/B tests
- -Sequential testing: Implement changes, measure for 30 days, compare to previous period - less rigorous but actionable
- -Bayesian testing tools: Tools like VWO's Bayesian calculator can give directional results with less traffic than frequentist tests
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With over a decade of experience in e-commerce optimization, Muhammed founded Growth Suite to help Shopify merchants maximize their conversion rates through intelligent behavior tracking and personalized offers. His expertise in growth strategies and conversion optimization has helped thousands of online stores increase their revenue.
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