Outlier Detection Rechner — Formel

How to Detect Outliers Using the IQR Method

Formula

IQR = Q3 - Q1

Lower Fence = Q1 - 1.5 * IQR

Upper Fence = Q3 + 1.5 * IQR

Values below the lower fence or above the upper fence are flagged as potential outliers. The 1.5 multiplier is Tukey's convention. Using 3.0 instead identifies extreme outliers.

Lösungsbeispiel

Q1 = 30, Q3 = 70. Is 95 an outlier?

  1. IQR = 70 - 30 = 40
  2. Lower fence = 30 - 1.5*40 = 30 - 60 = -30
  3. Upper fence = 70 + 1.5*40 = 70 + 60 = 130
  4. 95 is between -30 and 130, so it is NOT an outlier
  5. It would need to exceed 130 to be flagged