Hands-On Ensemble Learning with Python

What is variance?

Variance refers to how much individuals vary within a group. Again, variance is a concept from statistics. Taking a sample from a population, variance indicates how much each individual's value differs from the mean.

In machine learning, variance refers to the model's variability or sensitivity to data changes. This means that high-variance models can generally fit the training data well and so achieve high in-sample performance, but perform poorly out-of-sample. This is due to the model's complexity. For example, a decision tree can have high variance if it creates a rule for every single instance in the training dataset. This is called overfitting. The following figure depicts a decision tree trained on the preceding dataset. ...