It’s inconsistent.
In some cases, to be in the 10th percentile means ~10% of everyone is worse than you. You’re in the *bottom* 10%.
In other cases, to be in the 10th percentile means that ~90% of everyone is worse than you; you’re in the *top* 10%. Sometimes they specifically clarify “upper 10th percentile” but a lot of the time they don’t.
This is because *a lot* of people don’t understand math, so they use math words wrong, and those words end up taking on multiple, contradictory meanings in common use.
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