Which of the following is NOT a common analytics used to determine the winner of an AB test?

The lead conversion rate is indeed the correct choice as it is not typically considered a common analytical metric used directly to evaluate the outcomes of an A/B test. A/B testing primarily focuses on measuring the effectiveness of specific variables in campaigns, such as messaging, layouts, or calls to action, by assessing immediate interactions and engagement metrics.

Engagement score, click rate, and subject line tests measuring open rates are all metrics that provide insights into how recipients interact with the content during an A/B test. For instance, engagement scores help quantify overall interaction with marketing content, while click rates indicate how many users clicked on a specific link or call to action within the communication. Similarly, testing different subject lines in emails and measuring the open rate can directly reflect the effectiveness of those variations in capturing attention.

In contrast, lead conversion rate deals with the broader success of converting leads into customers, which can depend on various factors beyond the single interactions typically analyzed in A/B testing. This makes it less applicable in the immediate context of determining the "winner" in an A/B test where the focus is on specific elements of the campaign being tested.