An experimental method for measuring the true additional impact of a marketing activity by comparing outcomes between a group exposed to it and a similar control group that wasn't, isolating what actually happened *because* of the marketing versus what would have happened anyway.
Why it matters
A lot of marketing performance measurement can mistake correlation for causation — a customer who was going to convert anyway might simply be the one who happened to click an ad. Incrementality testing is specifically designed to answer the harder, more important question: did this marketing activity cause additional outcomes that wouldn't have happened otherwise?
In a sentence
"The incrementality test showed that a meaningful share of our retargeting 'conversions' would have happened anyway — the ads were reaching people who were already going to convert, not actually driving additional revenue."
Related terms
- Often confused with: Attribution (attribution assigns credit for a conversion across touchpoints that occurred; incrementality testing specifically measures whether the marketing activity caused an outcome that wouldn't otherwise have happened, using a control group — a channel can receive strong attribution credit and still show weak incrementality).