Which of the following is a best practice when implementing an experiment?

To ensure scientific accuracy and actionable results in a Google Ads experiment, you must test one variable for each experiment because isolating a single change—such as a different headline, call-to-action, or video length—allows you to pinpoint exactly which element caused the shift in performance. Testing multiple variables simultaneously creates "confounding factors," making it impossible to determine which specific adjustment led to the outcome, whereas a single-variable approach provides the clear data needed to make informed creative optimizations for future campaigns.