<b>Underpowered tests don't just miss real wins — when they hit, they exaggerate by 2-3x.</b>

<b>Underpowered tests don't just miss real wins — when they hit, they exaggerate by 2-3x.</b>
This is the winner's curse (Type M / magnitude error). With low power, only the luckily-large estimates clear significance, so every "win" is inflated.
— A 30%-powered test that shows +20% is probably a true +7% at best.
— Symptom: big lifts on small samples that shrink on re-test.
The smaller the sample behind a giant lift, the more you should discount it.
Read the number, not the story. [power ≈30% · Type-M ~2.5x]