What confidence level should I aim for (e.g., 95%)?

The industry standard confidence level for email A/B testing is 95%, meaning you accept a 5% probability of false positives (detecting a difference that does not exist).

90% confidence is acceptable for lower-stakes tests where you need directional guidance and can tolerate higher false positive risk. Useful for rapid iteration on non-critical elements.

99% confidence is appropriate for high-stakes decisions where acting on false positives would cause significant damage. Important for major strategy changes or irreversible decisions.

Higher confidence requires larger sample sizes or longer test durations. Match your confidence level to the decision's importance.

95% is the default for good reason. It balances statistical rigor with practical test duration. Deviate deliberately based on stakes, not convenience.