Variance is a prediction characteristic that tells us about the variability of model predictions; in other words, how big the range of output values can be. Usually, we use the term high variance or overfitting in the case when a model tries to incorporate many training samples very precisely. In such a case, the model cannot provide a good approximation for new data but has excellent performance on the training data.
The following graph shows the behavior of the polynomial regression model, with the polynomial degree equal to 15:
We can see that the model incorporates almost all the training data. Notice that the training data is ...
