Recently the EEC posted the results from a survey asking, “What is the primary metric by which you measure the success of your subject line A/B tests?”
42% –> Open rate
13% –> Click rate
18% –> Click-to-open rate
26% –> Conversion rate
There is no “right” answer. It varies by business, by situation, and by intent of the test being conducted. Each of these metrics measures something different and it is critically important to understand what is-in fact-being measured when each of these metrics is used to evaluate subject line A/B split tests.
Open rate: Here, I am referring to the unique number of emails that were opened as tracked from a tracking pixel divided by emails delivered. Open rate is the only way to answer the question “Which subject line will get the most people to open the email?” However, it says nothing about the how well the subject line leads into the content of the email itself.
Click rate: Taken alone, click rates measure the combined success of the subject line and the content contained within the email. In the evaluation of subject lines, it answers the question, “Which subject line works best with the content contained in my email to get subscribes to my site?”
Originally from “Subject Line Testing: What Metric Should You Use To Measure Success?”| Published July 23, 2008