In this episode of GrowthFit, Deborah O'Malley, founder of GuessTheTest, shares what thousands of real A/B-test case studies reveal about what actually wins — and the testing mistakes that quietly waste traffic.
After cataloguing hundreds of real experiments, Deborah's biggest lesson is humility: most "obvious" winners fail to replicate. The only reliable answer is to test on your own audience.
The test that won for them may lose for you. Context is everything.
She demystifies the stats debate — what each approach assumes, when each is appropriate, and why understanding your tool's method keeps you from shipping false winners.
Peeking early, underpowered samples, and ignoring the full purchase cycle top the list. Sample size and duration decide whether a result is real or noise.
Clarity, proof, and reduced friction win far more often than clever copy — but they still have to be validated, not assumed.
We feature D2C operators and CRO experts with a story worth sharing.
