What is k-fold cross-validation?
Updated May 17, 2026
Short answer
It splits data into k folds and evaluates model k times.
Deep explanation
Each fold is used once as test set while others form training set.
Real-world example
Used in small datasets to maximize training usage.
Common mistakes
- Data leakage across folds.
Follow-up questions
- What is stratified CV?
- Why k=5 or 10?