Encyclopedia of Database Systems

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


  • Ethan ZhangEmail author
  • Yi Zhang
Reference work entry
DOI: https://doi.org/10.1007/978-1-4614-8265-9_480


Precision measures the accuracy of an information retrieval (IR) system. More precisely, precision is the fraction of retrieved documents that are relevant. Consider a test document collection and an information need Q. Let R be the set of documents in the collection that are relevant to Q. Assume an IR system processes the information need Q and retrieves a document set A. Let |Ra| denote the number of documents that are in both R and A. Further let |R| and |A| be the numbers of documents in R and A, respectively. The precision of the IR system for Q is defined asP = |Ra|∕|A|.

Key Points

Precision and recall are the most frequently used and basic retrieval performance measures. Many other standard performance metrics are based on the two concepts.


Copyright information

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

Authors and Affiliations

  1. 1.University of CaliforniaSanta CruzUSA
  2. 2.Yahoo! Inc.Santa ClaraUSA

Section editors and affiliations

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