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Module 3: Classification and Prediction

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Which technique is particularly useful for reducing overfitting and obtaining a more reliable estimate of classifier performance?

(i) Cross-validation
(ii) Increasing noise
(iii) Data duplication
(iv) Removing the test set

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Solution

Correct Answer: (i) Cross-validation

Explanation

In k-fold cross-validation the data is split into k parts (folds). The model is trained on k-1 folds and tested on the remaining fold, repeating k times so every fold is used once for testing. The average score gives a more reliable estimate of performance, and because the model is tested on unseen data each time, it helps detect and reduce overfitting.

Why other options are incorrect:

  • (ii) Increasing noise - makes the model worse.
  • (iii) Data duplication - causes test data leakage and over-optimistic results.
  • (iv) Removing the test set - removes any way to measure performance on unseen data.

Answer: (i) Cross-validation

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