Ad optimization allows you to automatically split a campaign's impressions between test creatives.
Advertisers commonly produce many small variations on an ad, changing the background color, call to action, etc. These small changes can have a surprising impact on performance. Ad optimization controls which ad is selected once the DSP has determined that a campaign is eligible to bid on a given placement.
For example, say a campaign is eligible to bid on a 300x250 placement on cnn.com. Ad optimization then selects which of the available 300x250 ads to serve. It does this by dividing your ads into a control group and a test group. The control group is the current set of highest performing ads. The test group contains the lowest performing ads and any new ads that do not have adequate testing yet.
By default, 80% of the time, an ad from the control group is selected, and 20% of the time, an ad from the test group is selected. This ensures that most spend is for the best performing ads, while still allowing new ads to be tested. The number of ads that are in the control group can also be specified as a percentage of the total number of ads.
Enable ad optimization in the Advanced section on the campaign's General tab:
You can customize the way that your creatives are optimized by adjusting the Ad Optimization settings:
Goal – Choose your optimization metric: CTR or Conversion Rate. By default, creatives are optimized by CTR, because it’s typically the first metric with which creatives are judged and optimized.
Note: Conversion Rate optimization applies to clickthrough conversions only.
Evaluation Group – Before reaching the minimum Sample Size, ads must be evaluated in a default group. By default, all new creatives are evaluated in the Control Group, so that they can receive enough SOV, and thus impressions, to reach the minimum Sample Size.
Evaluation Period – The evaluation period dictates the length of time with which the Auto-Optimization uses to make decisions and determine confidence. Typically, the longer the Evaluation Period, the more accurate the optimization. The Evaluation Period is measured in 6-hour increments. By shortening the evaluation period, decisions will be made quicker, which might skew the accuracy of the optimization since the sample period is too short.
Sample Size – You can specify what you believe to be a significant sample size for optimization. This number should theoretically be higher for evaluating Conversion Rate, but for evaluating CTR, 10,000 is generally a good sample size for banner ads.
Control Group Size – “Control” is another word for highest-performing creatives. By default the best 20% of creatives are considered the “control group”. Lowering this setting reduces the amount of ads in the top-tier group, resulting in fewer “control” ads.
Control Group SOV – The Control Group SOV (share of voice) controls what percentage of impressions will be given to your best creatives. By default, 80% of traffic will go to the top-performing 20% of ads.