Percentage
A fraction expressed out of 100, written with the percent sign.
- Decimal × 100 = %; % / 100 = decimal.
- Percentage points ≠ percent change.
- Off-by-100 bugs come from mixing 0.85 vs 85.
When to use: Reporting accuracy, CTR, error rates, growth metrics.
Example: Accuracy 92% = 0.92 probability. 90% → 92% is +2 percentage points but +2.2% relative.