Why Your A-B Test Needs a Pre-Registration Log

In this episode of Conversion Rate Optimization with Fexingo, Lucas and Luna dive into the hidden pitfall of post-hoc analysis: why even a perfectly executed A-B test can lead you astray if you peek at the results before the sample size is reached. Using the real-world example of a travel-booking site that accidentally cut revenue by 8 percent after 'winning' a test early, they explain what a pre-registration log is, how it forces you to commit to one primary metric and one stopping rule, and why it saved a SaaS company from shipping a losing variant. Lucas walks through the simple spreadsheet template his team uses, and Luna pushes back on whether this adds too much process friction. They also discuss how pre-registration differs from a holdout group and why most CRO teams skip it — and why they shouldn't. A practical, gear-shifting episode for anyone running experiments that matter. #ABTesting #CRO #Marketing #ConversionRateOptimization #Experimentation #DataScience #PreRegistration #StatisticalRigor #TravelBooking #SaaS #PostHocAnalysis #SampleSize #PrimaryMetric #StopRule #FexingoBusiness #BusinessPodcast #LucasAndLuna #MarketingTips Keep every episode free: buymeacoffee.com/fexingo