Question: What's a best practice to follow when designing an experiment to test Performance Max campaigns?
- Create a new CPA or ROAS goal for Performance Max campaigns to achieve.
- Keep Performance Max budget limited to 10% of other campaigns’ budgets.
- Optimize Performance Max to a comparable CPA or ROAS target to other campaigns.
- Run the Performance Max experiment for one to two weeks before evaluating results.
or
- Run the Performance Max experiment for one to two weeks before evaluating results.
- Optimise Performance Max to a comparable CPA or ROAS target to other campaigns.
- Keep Performance Max budget limited to 10% of other campaigns' budgets.
- Create a new CPA or ROAS goal for Performance Max campaigns to achieve.
Explanation
Performance Max experiments should use comparable CPA or ROAS targets so results are evaluated against a fair performance benchmark. When targets are not aligned, the trial and control conditions may optimize toward different efficiency goals. Comparable targets help isolate the impact of the campaign setup rather than differences in bidding expectations. This makes the experiment results more useful for deciding whether to expand Performance Max.
Why the other options are incorrect
10% budget limit is not a stated best practice and may restrict the experiment from collecting enough performance data.
One to two weeks is too short for reliable evaluation because experiments need enough time and data to stabilize.
New CPA or ROAS goal can bias the test because the target should be comparable to other performance campaigns.
Source for verification
https://support.google.com/google-ads/answer/13826584
https://support.google.com/google-ads/answer/10724817
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