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ObsidianVault/Running Start/CSB320 - Machine Learning Concepts/Class 5-21 (Ensemble Models).md
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2026-05-21 18:33:15 -07:00

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- The average of guesses of a large number of people will typically be more accurate than an individual can be
- (wisdom of crowds)
- Bootstrapping
- generates simulated samples by sampling with replacement from existing sample
- sampling is random
- Out of bag sample
- data that was never picked in bootstrapping
- is often used for testing data (OOB samples were not in the training samples so the model has never seen them)
- with common techniques often ~30% of data is not picked (and forms OOB set)
- distribution of classes with bootstrapping will form a Gaussian distribution
- when enough samples are used bootstrap distributions will approximate population statistics
- Assumption is made with bootstrapping that the sample approximates the original population
- bootstrap samples are used as training sets, OOB samples serve as testing sets
```python
bootstrap_samples = [resample(df, replace=True, random_state=i) for i in range(5)]
```