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Performance & Measurement
4 min read
Incrementality testing measures the conversions your advertising truly caused — the ones that would not have happened without it — by comparing a group exposed to ads against a held-back control group. It cuts through attribution’s credit games to answer the only question that matters: did the ad actually add anything?
Split the audience. One group can see the ads; a control group cannot.
Run the campaign. Both groups are otherwise treated the same.
Compare conversions. The difference between them is the incremental lift.
Act on the truth. Fund what genuinely adds, cut what does not.
Geo tests. Hold back whole regions as the control.
Audience holdouts. Randomly exclude a share of users from ads.
Ghost ads. Log who would have been served, then compare.
PSA controls. Show a neutral ad to the control group.
Truth over credit. It measures cause, not just correlation.
Catches waste. It exposes spend that would have converted anyway.
Better decisions. It reallocates budget to genuine impact.
Scale needed. Reliable lift requires meaningful volume.
Complexity. Clean test design takes real discipline.
Opportunity cost. A holdout means some conversions go unserved.
Time. Lift can take weeks to read confidently.
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