Asked about Metrics and thresholds, worked through
What does it mean for a classifier to be calibrated, and when do you need it?
An answer that works
Its scores match observed frequencies: cases scored 0.3 are positive about 30% of the time. You need it whenever the score is used as a probability, such as in expected cost calculations or when showing risk to people.
Reading an answer is not being able to give one. The section that teaches this is Metrics and thresholds, worked through, 4 hours of Imbalanced and messy data.
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