- The classifier assigns the wrong class to the document, e.g. a type A page is classified as type B.
- The classifier fails to assign any class to the document.
- Precision is the ratio of documents that were assigned a specific class correctly to all of the documents that were assigned that class (i.e. the sum of documents that were correctly assigned that class and documents that were mistakenly assigned that class).

- Recall is the ratio of documents that were correctly assigned a class to all of the documents of that class.

