09/14/2026
Underfitting vs Overfitting π€π β two of the most important problems in machine learning, and your training vs validation loss can reveal which one youβre dealing with.
In this video, we break down:
π Underfitting β Training and validation loss are both high
π Overfitting β Training loss is low while validation loss rises
π§ How to fix underfitting:
β’ Increase model capacity
β’ Add useful features
β’ Reduce regularization
β’ Train longer if the model hasnβt converged
π οΈ How to fix overfitting:
β’ L1 and L2 regularization
β’ Dropout
β’ Early stopping
β’ More training data
β’ Data augmentation
π³ Bagging reduces variance by combining models trained on different data samples.
π Boosting primarily reduces bias by training models sequentially to correct previous errors.
The key idea:
Underfitting = not learning enough.
Overfitting = learning too specifically.
Understanding this bias-variance tradeoff is essential for building models that actually generalize to unseen data.