R Deep Learning Essentials - Second Edition

Types of evaluation metric

Different evaluation metrics are used for categorization and regression tasks. For categorization, accuracy is the most commonly used evaluation metric. However, accuracy is only valid if the cost of errors is the same for all classes, which is not always the case. For example, in medical diagnosis, the cost of a false negative will be much higher than the cost of a false positive. A false negative in this case says that the person is not sick when they are, and a delay in diagnosis can have serious, perhaps fatal, consequences. On the other hand, a false positive is saying that the person is sick when they are not, which is upsetting for that person but is not life threatening.

This issue is compounded when you ...