Machine Learning, Model Selection, Hyperparameter Tuning, Learning Curve, Cross Validation.
using the combined data of training and test set. Fig. 2: Illustration of 5-fold cross-validation. How many splits should we make, i.e., how should we choose K? Unfortunately, there is no free lunch, i.e., no single answer that always works best. If we choose K=N where N is the number of training