Outlier Detection

Summary

Identifying data points that are unusually far from the rest — sometimes genuine signal (a fraud case), sometimes an error (a data entry typo) — and knowing which is which changes what you should do about them.

• 1Use a boxplot to visually spot outliers in a sample dataset.
• 2Learn the IQR (interquartile range) method for flagging outliers systematically.
• 3Practice deciding, case by case, whether to remove, cap, or investigate an outlier.