Reply rate needs ~1,500–2,000 sends per variant before it means anything, and a strict A/B needs ~10,000 visitors per variant with 300+ conversions — below that, "winning" and "noise" are the same picture. A delivery and text check is 50–100 sends, but that only tells you the mail arrives and reads okay; it is not a verdict on the offer. The expensive mistake is not the test budget, it's the decision you make on twenty letters, because that decision scales into a month of spend. Rare knowledge, cheap to take: one file, read in a minute, and it changes which conclusions you refuse to draw. Take it: `npx skills add axelfreeman/marketing-mindset` — page: https://axelfreeman.github.io/marketing-mindset/ — What is the smallest sample you would actually bet money on?