Learn Python by Building Data Science Applications

Chapter 14

What is overfitting?

Many ML models (for example, decision trees) actively fit to perform well on the training set at hand, but at some point, this process goes beyond generalizable knowledge that's valuable for the task, with some parts being irrelevant to the test set. This is not only meaningless but will also affect the model's performance on other data. This phenomenon is known as overfitting, and there are ways to overcome it.

Why should we use cross-validation?

Cross-validation is a technique that's aimed at overcoming the issue of overfitting. In its basic form, it splits a training set into multiple folds, trains multiple models with the same settings on different combinations of those folds, and measures their performance ...