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EEE 598: Multimedia/Qos

Best library and internet resources plus literature searching techniques for your assignment.

Precision vs Recall: What's the Difference?

Precision vs Recall - different information needs - different searching techniques. 

retrieving what you need
retrieving all you need

Precision and recall are inversely proportional  

A high precision search ...

  • Finds few items (low recall) but most, if not all, will be exactly what you need.  
  • Can be as easy as typing in a few keywords and taking the top one or two results.
  • Takes relatively little time and effort. 
  • Information comes from only one or two authoritative sources.
  • Gives you the specific piece of information you need.
  • Used for finding facts, formulas and citations.

A high recall search ...

  • Finds many items; some will be exactly what is needed while the rest will contain only part of what is needed (low precision).
  • Requires extensive keyword, synonym, controlled vocabulary, author, and citation searching in multiple databases.  
  • Involves much time and effort. 
  • Information comes from multiple sources in multiple formats.
  • Gives you the reasonable expectation of having found everything.
  • Used for literature reviews and problem solving.  


When confronted with an information question, you need to decide how to balance the need for precision with the need for an appropriate level of recall.   The higher the recall needed, the more you need to employ good literature review skills. 

Good searching skills are important to employers

Knowing how to do a thorough literature review is not just "school work".   Whether you go into academics or work as a professional engineer, being able to find the necessary information efficiently is a highly desired skill and one that employers expect you to bring with you from college. 

Consider this excerpt from Head, Alison J.  Learning Curve: How College Graduates Solve Information Problems Once They Join the Workplace.  Project Information Literacy Research Report, the Passage Studies.  October 16, 2012.   p.24 

"The employers ... said they expected young hires to be patient but persistent researchers. 

Specifically, employers said they needed them to be capable of engaging co-workers in an interative research process, retrieving information in a variety of formats, identifying patterns in an array of sources, and diving into sources of information.

Yet these information competencies were rarely demonstrated ...     [young hires] had a tendency to respond too quickly with answers conventiently plucked form the nearest source.  At worst, [young hires] solved information problems with a lightning quick Google search, a scan of the first couple of page of results, and a linear answer finding approach."  


Those desired information skills mentioned by employers are the same ones used in high recall searching to ensure the necessary thoroughness: interative research process, variety of formats, array of sources, etc.  

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