Overfitting, L1 and L2 regularization, gradient descent variants, learning rates, Adam, early stopping and dropout.
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- What is overfitting?
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A model learns the training data too well, including noise, so it performs poorly on new unseen data.
- How does overfitting typically appear in a learning curve?
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Training error continues to decrease while validation error starts increasing.
- Name one common cause of overfitting.
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The model is too complex relative to the amount of training data.
- Why is a validation set critical for detecting overfitting?
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It estimates performance on unseen data independent of the training set.
- What term does L1 regularization add to the loss function?
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Lambda times the sum of absolute values of weights.
- What is L1 regularization also called?
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Lasso regularization.
- Which norm does L1 regularization minimize, the L1 or L2 norm?
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The L1 norm (sum of absolute values).
- What feature selection property does L1 regularization have?
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It can drive some weights exactly to zero, effectively removing features.
- How does L1 regularization penalize small weights versus large weights?
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It penalizes all weights equally per unit of magnitude.
- What term does L2 regularization add to the loss function?
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Lambda times the sum of squared weights.
- What is L2 regularization also called?
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Ridge regularization.
- Which norm does L2 regularization minimize, the L1 or L2 norm?
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The L2 norm (square root of sum of squares).
- How does L2 regularization affect weight magnitudes?
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It encourages all weights to be smaller but rarely drives them exactly to zero.
- In what scenario might L2 regularization be preferred over L1?
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When all features are potentially useful and you want to keep them all but reduce their magnitude.
- What is batch gradient descent?
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Computes gradients on the entire dataset before updating weights once per epoch.