metrics
Everything on Ground Truth tagged “metrics” — 2 items.
ROC curves and AUC: the number behind 'the detector works' Lesson
AUC measures how well a detector ranks positives above negatives across every possible threshold, which is why 0.5 means coin flip and why a high AUC can still hide a useless system.
Perplexity: the number that tells you a model still works Lesson
Perplexity measures how surprised a language model is by real text, expressed as the number of words it was effectively choosing between at each step -- lower means less confused, and a jump from single digits into the thousands means the model is broken.