Data Science Interview Question 7 |

Publicado em: 11 Junho 2023
no canal de: Programming Cradle

596

Bagging and boosting are both ensemble learning techniques used to improve the performance of machine learning models by combining multiple individual models. However, they differ in their approach and how they combine the models.

Bagging (Bootstrap Aggregating):

Bagging is a technique that involves training multiple individual models independently and then aggregating their predictions. The main steps in bagging are as follows:

Bootstrap Sampling: The training dataset is randomly sampled with replacement to create multiple subsets of the same size as the original dataset. Each subset is called a bootstrap sample.

Independent Model Training: Each bootstrap sample is used to train a separate model independently using the same learning algorithm.

Voting or Averaging: During the prediction phase, the predictions of all individual models are combined through voting (for classification problems) or averaging (for regression problems) to obtain the final prediction.

NOTE: The key idea behind bagging is to reduce the variance of the individual models by averaging or voting, which helps to improve the model's overall accuracy. The popular Random Forest algorithm is an example of a bagging ensemble method.

Boosting:

Boosting is a technique that iteratively builds a strong model by combining weak models. The main steps in boosting are as follows:

Sequential Model Training: The initial model is trained on the entire training dataset. During each subsequent iteration, the model focuses more on the instances that were misclassified or had high prediction errors in the previous iteration.

- Weighted Instance Importance: Each instance in the training dataset is assigned a weight. Misclassified instances or instances with higher errors receive higher weights, which makes them more influential in the subsequent iterations.

Sequential Model Combination: Each model is trained to minimize the errors of the previous models. The final prediction is obtained by combining the predictions of all models using weighted voting, where models with higher performance contribute more to the final prediction.

NOTE: The key idea behind boosting is to iteratively improve the model's performance by focusing on the instances that are difficult to classify correctly. Boosting algorithms, such as AdaBoost (Adaptive Boosting) and Gradient Boosting, are commonly used in practice.

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