What does recall measure in the validation statistics?

Recall is a crucial measure in the context of validation statistics, particularly when assessing the performance of a document review or classification system. It specifically indicates the effectiveness of the review process in identifying relevant documents from a larger set.

The measure of recall focuses on the proportion of actual positive instances that are correctly identified by the system. In the context of document review, recall quantifies the percentage of truly positive documents that were accurately retrieved and recognized by the review process. A high recall score implies that a significant number of relevant documents were caught, minimizing the chances of missing important information.

In contrast to the other options, which either address different metrics or concepts unrelated to recall, the focus on correctly identifying relevant documents directly aligns with the definition of recall. For instance, the error rate of the discard pile or the randomness of random sampling does not pertain to how effectively positive instances are recognized. Similarly, while the percentage of documents reviewed that are relevant may touch on recall-related themes, it does not accurately define what recall measures. Thus, the definition that emphasizes the identification of truly positive documents is the essence of what recall represents.