Encyclopedia of Database Systems

2018 Edition
| Editors: Ling Liu, M. Tamer Özsu

Precision at n

  • Nick Craswell
Reference work entry
DOI: https://doi.org/10.1007/978-1-4614-8265-9_484

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:
$$ \mathrm{Precision}\kern0.5em \mathrm{at}\kern0.5em \mathrm{n}=\frac{r}{n} $$
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Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Microsoft Research CambridgeCambridgeUK

Section editors and affiliations

  • Weiyi Meng
    • 1
  1. 1.Dept. of Computer ScienceState University of New York at BinghamtonBinghamtonUSA