Why is cross-validation important in model evaluation?

Cross-validation is crucial in model evaluation because it provides a more reliable assessment of model performance by testing the model on multiple independent subsets of data. This method involves partitioning the original dataset into several complementary subsets, training the model on a portion of the data, and validating it on the remaining part. By doing this multiple times, each datapoint has the opportunity to be in both the training and validation sets, which reduces the risk of overfitting to a specific dataset.

This independent testing is significant; it allows practitioners to gain insights into how the model is likely to perform on unseen data. Unlike simply evaluating the model on the training set, which can lead to overly optimistic performance metrics, cross-validation mitigates this risk by ensuring that model evaluation isn't biased by the same data used for training. As a result, it helps to produce a more generalized model that is better at making predictions on new, unseen data.