A metric is a quantitative measure used to monitor or assess model performance. Unlike a loss function, it does not optimize gradient descent directly; it helps determine whether training and model choices are improving. section 5.4.1
Use evaluation metrics to support practical model-development decisions:
- Monitor training progress and decide when further iterations stop providing enough benefit. section 5.4.1
- Compare feature selections and hyperparameter settings against a defined performance target. section 5.4.1 section 6.3
- Support systematic tuning by evaluating candidate settings within a cross-validation scheme that tests generalization. section 6.3
Tuning a boosting model
For an XGBoost model, first define one or more evaluation metrics, then specify the hyperparameter search space, choose cross-validation, and select a search strategy. The metrics compare candidate configurations and can also support early stopping during training. section 5.4.1 section 6.3















