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Turning Incrementality Tests Into Action That Makes You Money

Ecommerce Playbook · February 26, 2026 · 90 min

Summary

Incrementality tests are “in”… but the real problem is what you do after the read.In this episode, Taylor sits down with Olivia Kory (Chief Strategy Officer at Haus) and George Davis (CMO at Cozy Earth) to unpack the messiest part of modern measurement: operationalizing incrementality when results swing, channels conflict, and “platform ROAS” can’t be trusted.If you’ve ever asked:“Our holdout came back way lower than Meta… now what?”“Why don’t test results replicate month-to-month?”“How do I actually use an incrementality factor in real budget decisions?”“If everything is under 1.0 iROAS… should we cut spend or keep investing?”…this one is for you.What we coverWhy incrementality requires a holdout (and why “spend up / spend down” isn’t enough)The replication problem: why results change even with “clean” testsThe gap between measurement and optimization (platforms optimize for attribution, not incrementality)How operators use incrementality factors without letting them become a blunt instrumentWhy channel vs. channel is often the wrong fight (and why profit thresholds matter more)iROAS → IMR (Incremental Marginal Return): a more intuitive way to compare performanceBudget cadence: daily realities vs monthly allocation decisionsLong-term effects, “adstock” claims, and why post-treatment windows matterPractical levers that can improve results: creative, account structure, exclusions, distribution expansion (Amazon/retail)Got a weird incrementality result? Drop it in the comments. We’ll let you know what we’d do next.Read this next: CTC Core Methodology Series: Marketing Measurement - https://bit.ly/4tW2JwFShow Notes:Axon i

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