AI engineering glossary · Evaluation metrics
What is Youden's J statistic?
Youden's J statistic (also called Youden index): A single-number summary of a classifier at one threshold: J = sensitivity + specificity - 1. It ranges from 0 to 1 for a useful test. Picking the threshold that maximises J is a common way to choose the ROC point farthest above the chance diagonal.
Youden's J statistic: an example
With sensitivity 0.75 and specificity 0.99, J = 0.75 + 0.99 - 1 = 0.74.
Related terms
More Evaluation metrics terms
- Accuracy
- Accuracy paradox
- Adjusted Rand index
- AUC-ROC
- Average precision
- Balanced accuracy
- BERTScore
- Bits per byte
Where you learn it
Youden's J statistic is part of the AI Engineering Program, which teaches it with notes, a hands-on lab and an exam. The first lesson is free.