What is a primary metric in email marketing A/B testing?

• A. The click-to-open rate (percentage of recipients who clicked on links after opening an email)
• B. The bounce rate
• C. Open rate
• D. Time on site after click

Answer: (A)

The key idea is measuring how effectively an email compels action after someone has opened it. The best metric for this in email A/B testing is the click-to-open rate, which is the number of clicks divided by the number of opens. This metric directly ties the email content to the actual engagement you want—people clicking on links—while controlling for whether someone opened the email in the first place. Open rate alone can be influenced by subject lines and preheaders, and bounce rate just flags deliverability issues, not engagement with the content. Time on site after the click is useful for deeper analysis after the click, but it isn’t the primary measure of how well the email variation performs in driving clicks. So CTOR gives the clearest signal of content effectiveness in A/B tests.