What is a recommended practice when testing new content in an email campaign?

Isolating one variable to measure its performance is a recommended practice when testing new content in an email campaign because it allows you to clearly attribute any changes in performance metrics to that specific variable. By focusing on a single aspect—such as the subject line, content layout, or call-to-action—you create a controlled environment that ensures accurate results. This method enables you to understand the impact of each change effectively, making it easier to refine your email strategies based on data-driven insights.

The other approaches, such as changing multiple elements simultaneously or using the same subject line for both tests, can lead to confusion in the results as it becomes difficult to ascertain what specifically influenced the audience's reactions. Limiting the audience may reduce risks, but it can also constrain the sample size, leading to unreliable conclusions. Overall, isolating one variable is crucial for deriving actionable insights from your email campaign testing.