Guided Notes

Transform: Finding & Removing Outliers

Box plots and the Tukey rule, one- vs two-dimensional outliers, and removing aggregate rows that masquerade as outliers.

What is an outlier?

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An outlier is a value far from the rest of the data. It might be a genuine extreme (China's population), a data-entry error (a population of 12 billion), or a row that doesn't belong at all (the 'World' total mixed in with countries).

Outliers can distort averages and pull a regression line toward themselves. The data engineer's job is to find them and make removal possible; whether to remove them is usually a data scientist's decision.