Incrementality Testing
An experimental method that measures the true causal impact of a marketing activity by comparing outcomes between a group exposed to marketing and a control group that is not. Incrementality testing reveals whether marketing activities drive additional conversions or just capture ones that would have happened anyway.
Incrementality testing answers the fundamental question: did this marketing spend actually cause additional conversions, or would those conversions have happened without it? By randomly holding out a control group from seeing an ad or receiving a campaign, you can measure the true lift (incremental conversions) versus the baseline (conversions that occur without the marketing).
For growth teams, incrementality testing is the gold standard for marketing measurement because it establishes causation rather than correlation. Common applications include geo-based holdout tests for brand campaigns, PSA (public service announcement) tests for digital ads, and email holdout tests for lifecycle campaigns. The results often challenge conventional attribution data: channels that appear highly effective in attribution may show low incrementality because they are converting people who would have converted anyway. Run incrementality tests on your largest spend channels first to validate that budget is driving real impact. The practical challenge is sample size: you need sufficient volume to detect meaningful lift, which means incrementality testing works best for high-volume campaigns and channels.
Related Terms
Conversion Rate Optimization (CRO)
The systematic process of increasing the percentage of website visitors who take a desired action such as purchasing, signing up, or requesting a demo. CRO uses data analysis, user research, and A/B testing to improve conversion performance.
Conversion Funnel
A model representing the stages a user progresses through from initial awareness to completing a desired action. Each funnel stage narrows as some users drop off, and optimizing each stage's conversion rate improves overall throughput.
Landing Page
A standalone web page designed specifically to receive traffic from a marketing campaign and drive a single conversion action. Landing pages remove navigation distractions and focus entirely on persuading visitors toward one goal.
Call to Action (CTA)
A prompt that encourages users to take a specific next step, typically presented as a button, link, or form. Effective CTAs use clear, action-oriented language and create a sense of value or urgency to drive conversions.
Social Proof
Evidence that other people or organizations have chosen, endorsed, or benefited from a product or service. Social proof reduces purchase anxiety by showing prospects that peers have already validated the decision.
Value Proposition
A clear statement that explains how your product solves a customer's problem, what specific benefits it delivers, and why customers should choose it over alternatives. The value proposition is the foundation of all marketing messaging.