A/B Testing

A practical example

Example: an email marketer sends version A with a question subject line and version B with a stat-based line to 10,000 contacts each, then compares reply rates after both sends complete.

What to evaluate before investing

• Ask whether tests run simultaneously on randomized splits or sequentially, since sequential tests inherit seasonal bias.
• Check if the tool calculates statistical significance and required sample size, or leaves that math to you.
• Confirm you can define the primary metric in advance rather than picking the winner after the fact.

Limitations and tradeoffs

A/B tests only compare the two versions you built; insights may not transfer to other audiences, channels or seasons, so treat winners as provisional.