IRS13 Thesaurus, Phrase and Hierarchy Dictionaries chapter E. M. Keen Harvard University Gerard Salton Use, reproduction, or publication, in whole or in part, is permitted for any purpose of the United States Government. VII-21 Collection Dictionary Average Rank of Relevant and Input First Second Last IRE-3 Stem 4.4 11.6 334.0 Abstracts Thesaurus-3 5.2 11.2 251.8 CRAN-l Stem 7.8 13.0 72.0 Abstracts Thesaurus-3 4.5 9.7 65.5 CRAN-l Stem 6.4 14.8 53.3 Indexing Thesaurus-2 4.6 12.2 47.1 ADI Stem 8.3 12.6 36.7 Text Thesaurus-l 5.0 10.7 33.7 ADI Stem 8.1 15.7 39.2 Abstract Thesaurus-l 4.3 12.2 34.5 Comparison of Stem and Thesaurus Dictionaries Using Average Rank Positions of the First, Second and Last Ranked Relevant Documents, on Five Runs in Three Collections. Fig. 14