Incrementality: buyer questions answered
14 buyer questions about incrementality, each answered from the platforms' own help pages: a short answer, a step-by-step walkthrough with menu paths, and for some questions a version for one store type.
By Joris van Huët, Founder & CEOUpdated 4 min read
Run the numbers for your store: the free holdout test planner.
Each answer below takes one buyer question about incrementality and answers it from the platforms' own help pages, read on 1 October 2026. Read the short answer first. If you need to act in GA4, Shopify, Meta or Google Ads, the step-by-step version gives the menu paths.
The questions
What is incrementality testing?
- The short answer: What is incrementality testing?
- Step by step: How to run an incrementality test, step by step
- For one store type: What is incrementality testing for a fashion store?
How do I run a geo holdout test?
- The short answer: How do I run a geo holdout test?
- Step by step: How to run a geo holdout test, step by step
What is a conversion lift test?
- The short answer: What is a conversion lift test?
- Step by step: How to set up a conversion lift test, step by step
- For one store type: What is a conversion lift test for a sports nutrition brand?
How do I test if my ads are incremental?
- The short answer: How do I test if my ads are incremental?
- Step by step: How to test if your Meta ads are incremental, step by step
What is incremental revenue?
- The short answer: What is incremental revenue?
- Step by step: How to measure incremental revenue, step by step
- For one store type: What is incremental revenue for a health and beauty store?
How long should an incrementality test run?
- The short answer: How long should an incrementality test run?
- Step by step: How to pick an incrementality test length, step by step
What is a holdout group in marketing?
- The short answer: What is a holdout group in marketing?
- Step by step: How to set up a holdout group from your customer list
- For one store type: What is a holdout group for a home goods store?
Can a small store run incrementality tests?
- The short answer: Can a small store run incrementality tests?
- Step by step: How to run a small-store incrementality test, step by step
What is iROAS?
- The short answer: What is iROAS?
- Step by step: How to calculate iROAS from a lift test, step by step
- For one store type: What is iROAS for a pet products store?
How do I test if email is incremental?
- The short answer: How do I test if email is incremental?
- Step by step: How to run an email holdout test, step by step
How do I test branded search incrementality?
- The short answer: How do I test branded search incrementality?
- Step by step: How to test branded search incrementality, step by step
- For one store type: How do I test branded search for a food and drink store?
What is a matched market test?
- The short answer: What is a matched market test?
- Step by step: How to run a matched market test, step by step
How do I pause a channel to test it?
- The short answer: How do I pause a channel to test it?
- Step by step: How to pause an ad channel for a test, step by step
- For one store type: How should an electronics store pause a channel to test it?
What is the difference between lift and attribution?
- The short answer: What is the difference between lift and attribution?
- Step by step: How to compare lift and attribution, step by step
How to read these answers
Each answer opens with the short version in bold. Most then set one store's anonymised GA4 export next to the usual answer. That export describes one store, not a benchmark, and holds shares of revenue only.
Every other figure comes from a platform's own help page, linked inside the answer, or is a worked example labelled as one. Each answer ends with three checks you can run this week, with what a pass and a fail look like.
Check the homework. Your GA4 Attribution paths export already holds the evidence. Causality Engine reads that one file and shows what each channel caused next to what last-click gave it, in 1 to 2 minutes, for €99 once (excluding VAT), refundable within 30 days. Check the homework
Related answers
Frequently asked questions
Where do the facts in these incrementality answers come from?
From the platforms' own help pages, read on 1 October 2026 and linked inside each answer, and from one store's anonymised GA4 export. That export holds shares of revenue only, and it describes one store, not a benchmark.Which incrementality answer should I read first?
Start with the question closest to the decision in front of you. Read the short answer first. If you need to act in the platform, the step-by-step version gives the menu paths.Can I check these incrementality answers on my own store?
Yes. Every answer ends with three checks you can run this week in Shopify, GA4 or the ad platform, each with what a pass and a fail look like.
Go deeper: Causal attribution, explained.
Sixty-second versions of these ideas: Causality Engine on YouTube Shorts.
Keep reading
Terms in this article
- AttributionAttribution identifies user actions that contribute to a desired outcome and assigns value to each. It reveals which marketing touchpoints drive conversions.
- CausalityCausality is the relationship where one event directly causes another, essential for identifying specific actions that drive desired outcomes in marketing.
- ConversionConversion is a specific, desired action a user takes in response to a marketing message, such as a purchase or a sign-up.
- Google AdsGoogle Ads is an online advertising platform where advertisers bid to display ads, service offerings, and product listings.
- Holdout TestA holdout test is an experiment where a portion of the audience does not see a campaign. This measures the campaign's true incremental impact.
- IncrementalityIncrementality measures the true causal impact of a marketing campaign. It quantifies the additional conversions or revenue directly from that activity.
- Incrementality TestingIncrementality Testing measures the additional impact of a marketing campaign. It compares exposed and control groups to determine causal effect.
- Lift TestLift Test: An experiment designed to measure the incremental impact of a marketing campaign by comparing a test group to a control group.