Statistical power
In practice, for a UK buyer
The paragraph above is the neutral answer. This is the part a vendor glossary leaves out.
The concept that separates measurement from theatre, and the one almost no media platform surfaces. AdBuyMCP computes it before running a lift test, defaulting to 80% power at 5% significance on daily observations, and refuses to proceed when the design falls short — returning the days of post-exposure data the test would actually need and the minimum lift it could detect. The refusal is the feature: an underpowered result is not a weak answer, it is a random one, and a random number in a board pack is indistinguishable from a real one.
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.
Minimum detectable effect (MDE)
The smallest true effect a test could reliably detect, given its sample size, the variance in the data and the power the design was set to. Effects smaller than the MDE will usually be missed even when they are real.
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.
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