📖 Introduction
- Gradient Descent
- First-order iterative optimization algorithm for finding a local minimum of a differentiable function.
![](https://velog.velcdn.com/images/araseo/post/b2894f8f-dd48-4954-9877-4f9078333745/image.png)
📖 Generalization
- How well the learned model will behave on unseen data.
![](https://velog.velcdn.com/images/araseo/post/5210773a-6eba-43b5-9907-ef9638a24567/image.png)
📖 Underfitting vs. Overfitting
![](https://velog.velcdn.com/images/araseo/post/473b2e44-12be-4ee1-a0c4-ebf2d07c3c72/image.png)
📖 Cross-validation
- Cross-validation is a model validation technique for assessing how the model will generalize to an independent (test) data set.
![](https://velog.velcdn.com/images/araseo/post/abf44177-9ef7-478a-951c-9de12cc62162/image.png)
📖 Bias and Variance
![](https://velog.velcdn.com/images/araseo/post/3b407b47-15d7-4384-af52-8bc52a7792d3/image.png)
📖 Bias and Variance Tradeoff
![](https://velog.velcdn.com/images/araseo/post/ca949a04-fe9c-477c-bac3-4bde82f0d640/image.png)
- We can derive that what we are minimizing (cost) can be decomposed
into three different parts: bias2, variance, and noise.
![](https://velog.velcdn.com/images/araseo/post/bff291c8-536d-4b77-8b63-9d81990fec5f/image.png)
📖 Bootstrapping
![](https://velog.velcdn.com/images/araseo/post/5ac836b0-388d-4b9b-a246-639118f96bc1/image.png)
- Bootstrapping is any test or metric that uses random sampling with replacement.
📖 Bagging vs. Boosting
- Bagging (Bootstrapping aggregating)
- Multiple models are being trained with bootstrapping.
- ex) Base classifiers are fitted on random subset where individual predictions are aggregated (voting or averaging).
- Boosting
- It focuses on those specific training samples that are hard to classify.
- A strong model is built by combining weak learners in sequence where each learner learns from the mistakes of the previous weak learner.
![](https://velog.velcdn.com/images/araseo/post/45610afa-4dc9-459f-b3c6-aaf4ec2b1084/image.png)
<이 게시물은 최성준 교수님의 '최적화의 주요 용어 이해하기' 강의 자료를 참고하여 작성되었습니다.>
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