subtopic

Generalisation, overfitting and underfitting (build it)

Fit polynomial degrees 1–15 of load vs temperature and decision-tree depths 1–20 on German Credit; plot train vs validation error. Concepts: Generalisation; overfitting; underfitting; bias–variance trade-off; validation curve Project A: Tree depth 1–20: watch validation ROC-AUC peak around depth 3–6 and then drop. Project B: Polynomial degree 1–15 on temperature → load: degree 2–3 captures the U-shape; degree 15 wiggles.

Builds on: B17 · Build: Fit a Line with Gradient Descent (calculus in action)