Outlier Detector (IQR, Z-score & MAD)

The IQR rule flags values below Q1 − 1.5·IQR or above Q3 + 1.5·IQR. The z-score rule flags |z| > 3. The modified z-score uses the median absolute deviation (MAD): M = 0.6745 × (x − median) ÷ MAD, flagging |M| > 3.5, which is robust to the outliers themselves.