27 June 2026
Splitting one long checkout into 3 short steps changes conversion by roughly ±0%. The step count is mostly a wash; what moves the number is perceived progress and how many fields survive, not how many…
26 June 2026
Counting conversions per session instead of per user can swing a result by 10%+. Users with multiple sessions get counted multiple times, and heavy users skew toward whichever arm they landed in more.…
25 June 2026
Underpowered tests don't just miss real wins — when they hit, they exaggerate by 2-3x. This is the winner's curse (Type M / magnitude error). With low power, only the luckily-large estimates clear sig…
24 June 2026
Running two A/B tests on the same page at once can silently corrupt both. If the button-color test and the headline test interact, each contaminates the other's control group. You read two clean wins …
23 June 2026
Testing 20 metrics at 95% gives you a ~64% chance of at least one false win. Every extra metric you eyeball is another coin flip against you — the multiple-comparisons problem. — Declare one primary m…
22 June 2026
One in five "successful" CRO wins quietly damages a metric nobody was watching. Aggressive checkout simplification lifts conversion but raises refund and chargeback rates — the cost lands in a differe…