What is the purpose of "train-test splits" in machine learning?

The purpose of "train-test splits" in machine learning is to evaluate model performance on unseen data. This process involves dividing a dataset into two distinct sets: one set is used for training the model, while the other set is reserved for testing its performance. The training set helps the model learn patterns and relationships within the data, while the test set allows for the assessment of how well the model generalizes to new, unseen data.

This evaluation is crucial because it helps to determine the model's accuracy and efficiency in making predictions outside of the training data. By assessing the model on data it has not encountered before, practitioners can gain insights into its real-world applicability and reliability, which is a fundamental aspect of the model validation process.

In contrast, combining different datasets, optimizing hyperparameters, and increasing the training dataset size serve different functions in machine learning and do not specifically address the need for evaluating model performance on new data.