Exam Professional Machine Learning Engineer topic 1 question 48 discussion

This ref doesn't explain WHY we should use NCV in this case - it just explains HOW to use NCV when dealing with time series. Cross-validation, including nested cross-validation, is a powerful tool for model evaluation and hyperparameter tuning, but it does NOT DIRECTLY ADDRESS data leakage. Data leakage refers to a situation where information from the test dataset leaks into the training dataset, causing the model to have an unrealistically high performance. Nested cross-validation can indeed help provide a more accurate estimation of the model's performance on unseen data, but IT DOESN'T SOLVE the underlying issue of data leakage if it's already present.

I agree. Besides, when a CV is done randomly (not split by the time point) it can make things worse.

The book mentions cross-validation.. NOT 'nested cross-validation' (page 34), however this answer is better than C. you want to remove value that are NOT correlated versus correlated as in answer C. ;)

Option B: Nested cross-validation is primarily used to estimate model performance accurately and select the best model hyperparameters. While it's a good practice, it doesn't directly address the overfitting issue. It helps prevent over-optimistic model performance estimates but doesn't necessarily fix the overfitting problem. Option C: Removing features highly correlated with the target value can be a valid step in feature selection or preprocessing. However, it doesn't directly address the overfitting issue or explain why the model is performing exceptionally well on the training data. It's a separate step from mitigating overfitting. Option D: This option is incorrect. Tuning hyperparameters should aim to improve model performance on the validation set, not reduce it. In summary, the most appropriate next step is Option A: