Holdout
In practice, for a UK buyer
The paragraph above is the neutral answer. This is the part a vendor glossary leaves out.
The most common way a lift test quietly measures nothing is a contaminated holdout: the control markets received some of the campaign, so the comparison is exposed-versus-slightly-less-exposed. AdBuyMCP checks for this before the readout rather than after, and refuses with a specific instruction — exclude those markets from targeting for the test window, or nominate a control the campaign does not buy.
What this one connects to
Most confusion in media buying comes from two adjacent terms being used interchangeably, so these are the neighbours worth reading next.
Geo-lift test
An experiment that runs advertising in some geographic markets and withholds it from comparable others, then compares outcomes between them. The causal design that needs no login, pixel or match rate.
Incrementality
The share of an outcome that happened because of the advertising, measured against what would have happened anyway. Measured by comparing an exposed group with a comparable unexposed one, not by counting conversions that followed an advert.
Matched market
A control market chosen because its historical outcome pattern closely tracks the test market's, so that a later divergence can be attributed to the campaign.
More on measurement and evidence
What you can prove afterwards, and the difference between a number that means something and a number that does not.
45 minutes. Bring a real brief and we compile it live. You describe one audience and watch it compile into seven targeting specifications, each with the score for how much of the definition survived.
Talk it through