Question at position 39 Multiple Choice Question: Which of the following is NOT an advantage of cross-validation over simple train-test split? It utilizes the data more effectively than a single train-test split.It reduces the sensitivity of the model's performance to the train-test split.It provides the distribution of a metric to evaluate the model's performance.It always improves the model's generalization to unseen data.

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BlackTom AI · Accepted Answer

To analyze this question, I will evaluate each statement about cross-validation (CV) and distinguish which one does not describe an advantage over a simple train-test split.
Option 1: 'It utilizes the data more effectively than a single train-test split.' This is true. CV, by repeatedly training on different subsets and validating on hold-out parts, makes fuller use of the available data for both training and evaluation, compared with a single split that discards a portion of data for testing.
Option 2: 'It reduces the sensitivity of the model's performance to the train-test split.' This is also true. Since CV averages performance across multiple partitions, results are less dependent on a particular random split, reducing variance due to split choice.
Option 3: 'It provides the distribution of a metric to evaluate the model's performance.' This is correct. CV yields a distribution (e.g., a set of scores across folds), which offers insight into variability and reliability of the model's performance rather than a single point estimate.
Option 4: 'It always improves the model's generalization to unseen data.' This is the statement that is not necessarily true. While CV offers better estimates and reduces overfitting risk, it does not guarantee that the model will generalize better to truly unseen data in practice. The chosen model, hyperparameters, and data distribution still determine generalization, and CV can even lead to optimistic tuning if used improperly (e.g., leakage, inappropriate preprocessing). Therefore, this claim overstates CV's guarantees.
In summary, options 1–3 describe accurate advantages of cross-validation, whereas option 4 makes an absolute claim about generalization that CV does not guarantee in all scenarios.

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