AI engineering glossary · ML fundamentals
What is test set?
Test set (also called Held-out test set): Data reserved for one final, honest estimate of how the chosen model performs on unseen cases. It must not influence training or tuning decisions in any way. If you keep peeking at it and adjusting, its estimate becomes too optimistic.
Test set: an example
After choosing a model using validation results, you score it once on the 1,500 untouched test emails and report that accuracy.
Related terms
More ML fundamentals terms
- Time-series split
- Train-test contamination
- Training
- Training error
- Training example
- Training set
- Transfer learning
- True risk
Where you learn it
Test set is part of the AI Engineering Program, which teaches it with notes, a hands-on lab and an exam. The first lesson is free.