Synonyms
P@n
Definition
In an information retrieval system that retrieves a ranked list, the top-n documents are the first n in the ranking. Precision at n is the proportion of the top-n documents that are relevant.
Key Points
If r relevant documents have been retrieved at rank n, then:
The value of n can be chosen based on an assumption about how many documents the user will view. In Web search a results page typically contains ten results, so n = 10 is a natural choice. However, not all users will use the scrollbar and look at the full top ten list. In a typical setup the user may only see the first five results before scrolling, suggesting Precision at 5 as a measure of the initial set seen by users. It is the document at rank 1 that gets most user attention, because this is the document that users view first, suggesting the use of Precision at 1 (which is equivalent to Success at 1).
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© 2018 Springer Science+Business Media, LLC, part of Springer Nature
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Craswell, N. (2018). Precision at n. In: Liu, L., Özsu, M.T. (eds) Encyclopedia of Database Systems. Springer, New York, NY. https://doi.org/10.1007/978-1-4614-8265-9_484
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DOI: https://doi.org/10.1007/978-1-4614-8265-9_484
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Publisher Name: Springer, New York, NY
Print ISBN: 978-1-4614-8266-6
Online ISBN: 978-1-4614-8265-9
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