To give an extreme example of overfitting, let's say you have a test set which has these examples: B -> 11, H -> 5, M -> 11. Well, you can solve these easily.

To give an extreme example of overfitting, let's say you have a test set which has these examples: B -> 11, H -> 5, M -> 11. Well, you can solve these easily. Just make a function like this: function solve(letter) { return {B: 11, H: 5, M: 11}[letter]; } machine learning 4Head . Of course, the point is to solve for examples you haven't seen yet, so this "solution" isn't amusing anyone. That said, overfitting commonly happens even without trying to overfit, and people use techniques to minimize it.