<b>Testing 20 metrics at 95% gives you a ~64% chance of at least one false win.</b>

<b>Testing 20 metrics at 95% gives you a ~64% chance of at least one false win.</b>
Every extra metric you eyeball is another coin flip against you — the multiple-comparisons problem.
— Declare one primary metric before launch. Everything else is exploratory and needs replication.
— If you must track many, correct the threshold (Bonferroni, Benjamini-Hochberg).
The "interesting secondary finding" is usually the false positive you went looking for.
Read the number, not the story. [1−0.95^20 ≈ 64%]