over-sampling minority class
**Over-Sampling Minority Class** is the **simplest technique for handling class imbalance** — duplicating or generating additional samples from the minority class to increase its representation in the training set, ensuring the model receives sufficient gradient signal from rare classes.
**Over-Sampling Methods**
- **Random Duplication**: Randomly duplicate existing minority samples — simplest approach.
- **SMOTE**: Generate synthetic samples by interpolating between nearest minority neighbors.
- **ADASYN**: Adaptively generate more synthetic samples in regions where the minority class is underrepresented.
- **GAN-Based**: Use GANs to generate realistic synthetic minority samples.
**Why It Matters**
- **No Information Loss**: Unlike under-sampling, over-sampling preserves all training data.
- **Overfitting Risk**: Exact duplication can cause the model to memorize minority examples — augmentation mitigates this.
- **Semiconductor**: Rare defect types need over-sampling — a model that ignores rare defects is operationally dangerous.
**Over-Sampling** is **amplifying the rare signal** — increasing minority class representation to ensure the model learns from every class.