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What is the difference between bagging and boosting algorithms? Provide examples of each.

Revati S Misra29128-May-2023

What is the difference between bagging and boosting algorithms? Provide examples of each.

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Updated on 29-May-2023
Revati S Misra

Revati S Misra

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Aryan Kumar

Aryan Kumar

29-May-2023

Bagging and boosting are both ensemble learning techniques used to improve the performance of machine learning models. However, they differ in their approach to combining multiple models. Here's an explanation of the differences and examples of each:

Bagging (Bootstrap Aggregating): Bagging is a technique where multiple models are trained independently on different subsets of the training data and their predictions are combined through averaging or voting. The subsets of data are created through a process called bootstrapping, which involves randomly sampling the training data with replacement.

Key characteristics of bagging include:

  1. Independence: Each model in the ensemble is trained independently of the others.
  2. Sampling with Replacement: The training data is randomly sampled with replacement to create different subsets for each model.
  3. Parallel Training: Models in a bagging ensemble can be trained in parallel since they are independent.
  4. Voting or Averaging: The predictions of individual models are combined by majority voting (for classification) or averaging (for regression) to make the final prediction.
  5. Example Bagging Algorithm: Random Forest Random Forest is a popular bagging algorithm that uses decision trees as the base models. It creates an ensemble of decision trees, where each tree is trained on a different subset of the training data using a random selection of features. The final prediction is made by aggregating the predictions of all the decision trees.
  6. Boosting: Boosting is a technique where multiple models, usually weak learners, are trained sequentially, and each subsequent model focuses on correcting the errors made by the previous models. In boosting, the models are trained in iterations, and each iteration assigns higher weights to the misclassified instances, emphasizing their importance in subsequent iterations.

Key characteristics of boosting include:

  1. Sequential Training: Models are trained sequentially, and each subsequent model focuses on the misclassified instances from previous iterations.
  2. Adaptive Weighting: Instances that are misclassified receive higher weights, allowing subsequent models to pay more attention to them.
  3. Weighted Voting: Each model's prediction is weighted based on its performance and combined to make the final prediction.
  4. Example Boosting Algorithm: AdaBoost AdaBoost (Adaptive Boosting) is a well-known boosting algorithm. It starts by training a weak learner on the original training data. In subsequent iterations, the misclassified instances from the previous iteration are given higher weights, and a new weak learner is trained to focus on these instances. The final prediction is made by combining the predictions of all the weak learners, with each learner's contribution weighted based on its accuracy.

In summary, bagging creates an ensemble of models by training them independently on different subsets of data and averaging or voting their predictions. Boosting, on the other hand, sequentially trains models by focusing on misclassified instances and assigning them higher weights. The final prediction is made by combining the predictions of all the models, with each model's contribution weighted based on its performance.

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