The effectiveness of an information retrieval system is usually determined by the ratios precision and recall. Precision indicates how well the retrieved documents match a user’s interest. It is the ratio of the number of relevant documents retrieved to the total number retrieved:
Recall is the ratio of number of relevant documents retrieved to the total number of relevant documents in the collection:
These ratios can also be used to determine the effectiveness of a recommender system. Precision provides an indication of the quality of the recommendations. Recall gives an indication of how many documents are recommended from the total number of relevant documents.
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