• Running the Performance Max experiment 1-2 weeks before evaluating results
• Setting an altogether new CPA or ROAS goal for Performance Campaigns
• Limiting the Performance Max budget to 10% of other campaigns’ budgets
• Setting the Performance Max CPA or ROAS target to a level comparable to other campaigns

The correct answer is: Setting the Performance Max CPA or ROAS target to a level comparable to other campaigns

Explanation: When developing an experiment for testing Performance Max campaigns, it is best to set the Performance Max CPA (cost per acquisition) or ROAS (return on ad spend) target to a level comparable to other campaigns. In the pre-test phase, it’s crucial to optimize campaigns to the same conversion goals as your Performance Max campaign. After the test, examine the change in overall conversions or conversion value at a similar CPA/ROAS between Performance Max and other campaigns. Remember to account for differences in CPA/ROAS targets when comparing pre- and post-periods performance. Employ pre-post testing methodology or A/B experiments to evaluate the success of Performance Max campaigns.