What should you consider before running an A/B test on a live campaign?

• A. The experiment may impact the performance of the existing campaign
• B. The experiment will always improve performance
• C. It will have no impact on the existing campaign
• D. It will automatically optimize bidding

Answer: (A)

When you run an A/B test on a live campaign, the most important thing to consider is that the experiment can affect the performance of the existing campaign. Splitting traffic between variants changes how impressions, clicks, and spend are distributed, which can shift metrics like CPA, ROAS, CTR, and overall volume. It can also disrupt the learning phase of automated bidding and ad delivery, potentially altering quality scores and auction dynamics. Because of this, you need a solid plan: ensure proper randomization and isolation of variants, define a statistically valid sample size and duration, keep everything else constant except the variable you’re testing, and account for time-of-day and day-to-day fluctuations to avoid biased results. The test won’t necessarily improve performance and may even hurt it, it can have measurable effects on the current campaign, and bidding isn’t automatically optimized just by running the test.