Machine Learning
Interview Questions
πŸ”’ Cross-validation

What is cross-validation, and why is it important?

Cross-validation is a technique used to evaluate the performance of a machine learning model by using a limited amount of data. It involves splitting the available data into a training set and a validation set, then using the training set to train the model and the validation set to evaluate its performance. The process is repeated multiple times with different splits of the data, and the results are averaged to get an estimate of the model's performance.

The main advantage of cross-validation is that it provides a more reliable estimate of the model's performance, especially when working with small datasets or imbalanced datasets. It also helps prevent overfitting by providing a more accurate assessment of the model's ability to generalize to new data.

One common type of cross-validation is k-fold cross-validation, which involves dividing the data into k subsets or folds of approximately equal size. The model is then trained k times, each time using a different fold as the validation set and the remaining folds as the training set. The results from each fold are averaged to get the final estimate of the model's performance.

While cross-validation can be time-consuming and computationally expensive, it is an important technique for ensuring the reliability of machine learning models. It helps to identify issues such as overfitting, underfitting, and data leakage, which can have a significant impact on the model's performance in the real world.


  • Provides a more reliable estimate of the model's performance
  • Helps prevent overfitting
  • Can help identify issues such as underfitting and data leakage
  • Useful for small or imbalanced datasets


  • Can be time-consuming and computationally expensive
  • May not work well with certain types of data, such as time series data