CRANV2 Methods for presentation of results chapter Cyril Cleverdon Michael Keen Cranfield An investigation supported by a grant to Aslib by the National Science Foundation. Use, reproduction, or publication, in whole or in part, is permitted for any purpose of the United States Government. - 66 - Starting Term Groups 2/3 4 5 6 7 8 9 10 11 12/15 Twelve Coordination Levels 1 1 1 1 1 1 1 1 1 1 2 3 1 1 1 1 1 1 1 1 I 2 3 4 i 1 1 1 i 1 1 1. 2 3 4 5 i 1 I 1 1 1 1 2 3 4 5 6 1 1 1 1 1 1 2 3 4 5 6 ? 1 1 1 1 1 2 3 4 5 6 7 8 1 1 1 1 2 3 4 5 6 7 8 9 1 1 1 2 3 4 5 6 7 8 9 10 1 1 2 3 4 5 6 7 8 9 10 11 1 2 3 4 5 6 7 8 9 I0 ii 12 FIGURE 3.28T GROUPINGS FOR MAXIMUM STARTING TERM COORDINATION LEVELS FOR METHOD 3 All methods discussed so far have results which, at higher coordination levels, are based on increasingly smaller sets of questions. Method 4 overcomes this particular drawback, by totalling all questions at the highest coordination levels that retrieve documents in every question. Known asthe method of 'maximum retrieving term coordination levels', all questions are first aligned at the highest coordination level at which, in every question, at least one document is retrieved, irrespective of whether or not it is relevant. This level will vary from question to question, and by referring back to Fig. 3.20T, it can be seen that in the particular conditions of that test, some questions only began retrieving documents when several of their starting terms had been dropped off in coordination. For example, none of the twelve starting- term questions retrieved documents at a coordination level higher than nine. When the search results have been aligned by the coordination level at which each question gives a result, the figures are totalled, the coordination.level in each question being relaxed one term at a time, until every question is reduced to a single term search. The results by this method are given in Fig%,30T, and the curve p]otted in Fig. 3.30P. It will be noted tha[OCRerr] the lower end of the curve terminates at 17% recall and 22% precision; this po.int has been derived from the individual results