Was It Actually Incremental? A Practical Guide to Measuring Incrementality in Marketing

Speakers: Lisa Combs and Charlotte Bourne

Roles: Data Scientists, Marketing Analytics, Expedia Group

Marketing teams spend big budgets on campaigns, loyalty programmes, and media, but how do we know if any of it actually caused the desired outcome or just coincided with it? In this session, we introduce the core challenge of incrementality measurement: separating genuine causal lift from noise, seasonality, and other effects.

We walk through the methods used in industry, including marketing mix models, randomised A/B tests, geo-based holdout experiments, marketing attribution, and pre/post analysis. We cover what each is used for as well as its limitations. This session is hands-on, so we will review real Expedia Group investment decisions and how our team decides which method to use under genuine statistical uncertainty. No marketing background needed, only curiosity about causal thinking.

About the speakers

Lisa Combs

• Lisa is a Data Scientist III in Expedia Group's Media & Communication Analytics team in London. She measures the impact of media and sponsorships investment on the business.
• Lisa joined Expedia Group in 2025 and works with incrementality testing and marketing mix modelling to help teams decide where media spend delivers real value.
• Lisa also has experience working in the public sector as well as the consulting and payments industries.

Charlotte Bourne

• Charlotte is a Data Scientist II in Expedia Group’s Traveler Engagement and Loyalty Analytics team, where she has spent most of her career since joining as a Graduate in 2023.
• Charlotte applies analytics and experimentation to loyalty and customer questions, measuring how EG’s loyalty programmes perform and what drives member behaviour.
• Charlotte also has experience working as a Statistician in the pharmaceutical industry.