IRS13 Word-Word Associations in Document Retrieval Systems chapter M. E. Lesk Harvard University Gerard Salton Use, reproduction, or publication, in whole or in part, is permitted for any purpose of the United States Government. IX-43 Request improved by Request not association over null improved by association Request improved by 16 8 24 indexing over null Request not improved 18 by indexing over null 9 9 25 17 42 a) Improvements of Association Methods over Indexing Request greatly Request not improved by greatly improved association by association Request greatly (rank recall up .1) 4 5 9 improved by indexing Request not greatly 23 33 improved by indexing 10 14 28 42 b) Large Improvements of Association Metnods over Indexing Contingency Tables for Co-Variation of Indexing and Association Methods Table 13