Regression, classification Train/learn/fit f from data (model) Score: for new x, get f(x) Algos: LR, k-NN, DT, RF, GBM, NN/DL, SVM, NB… Goal: max acc/min err new data Metrics: MSE, AUC (ROC) Bad: measure on train set. Need: test set/cross-validation (CV) Hyperparameters, model capacity, overfitting Regularization Model selection Hyperparameter search (grid, random) Ensembles