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Table 2 Tuning a search engine to attain two different scenarios of retrieval.

From: Relemed: sentence-level search engine with relevance score for the MEDLINE database of biomedical articles

Scenario 1. Query with specificity of 99.99% is insufficient for a database of 16 million records.
   The truth  
   relevant records irrelevant records  
search engine records returned to user 495 1,600 2,095
  records eliminated 5 15,997,900  
   500 15,999,500 16,000,000
odds ratio 1,000,000.00    
Specificity 99.99%    
sensitivity (recall) 99.01%    
Precision 23.63%    
Scenario 2. The price for a very high specificity: Missing a large number of relevant records.
   The truth  
   relevant records irrelevant records  
search engine records returned to user 250 16 266
  records eliminated 250 15,999,484  
   500 15,999,500 16,000,000
odds ratio 1,000,000.00    
Specificity 99.9999%    
sensitivity (recall) 50.00%    
Precision 93.99%