Reference · Glossary
Cross-validation
Splitting data into **multiple train/test folds** so you estimate performance more reliably than a single lucky split.
When to use
Small tabular datasets, hyperparameter tuning, and student labs before trusting one accuracy number.
When not to
Massive streaming data at scale — simpler holdout or time-based splits may suffice.
Example
5-fold CV: train on 4 chunks, test on the 5th, rotate — report average accuracy across folds.