Optimizing email performance requires empirical experimentation grounded in statistical significance to ensure measured differences are not random noise.
1. Calculating Sample Size & Test Duration
📐 Statistical Confidence Mandate
Enforce a minimum 95% confidence level (p-value < 0.05) with at least 500 conversions per variant before declaring a winning email template or subject line.
| Test Variable | Primary Evaluation Metric | Minimum Sample Size per Variant |
|---|---|---|
| Subject Line & Preheader | Unique Open Rate | 5,000 subscribers |
| Call-to-Action (CTA) Placement | Click-Through Rate (CTR) | 8,000 subscribers |
| Send Time & Day Optimization | Click-to-Open Rate (CTOR) | 10,000 subscribers |
| Personalization Token Strategy | Conversion Rate / Revenue per Recipient | 15,000 subscribers |