CRANV2 Conclusions 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. - 261 - Document Index Number Terms 1 ADx 2 AIBIDlX 3 ACDlx 4 BlX 5 BCDAlx 6 ClX 7 BClX 8 DlX 9 ABCDx 10 AlX 11 BDAlx 12 ClX 13 AB1ClX 14 D x 15 B[OCRerr] Dx 16 Dx 17 C[OCRerr]1 BI x 18 ClX 19 Ax 20 BlX Assuming the search now is for any coordination of (A + A1), (B + (C + C1) and (D + D1), the retrieval at different coordination levels willBlbe)' as follows Coordination Level No. of Documents Retrieved 2 (Document 5, 9) 8 (Document 5. 9. 2, 3, 11. 13. 15. 17) 10 (Document 5. 9. 2, 3, 11, 13. 15, 17. 1, 7) 20 (Document 5, 9, 2, 3. 11, 13. 15, 17, 1, 7, 4, 6, 8, 10, 12, 14, 16, 18, 20) Again it is shown that the sum of the retrievals (40) equals the total postings for the four groups of terms. Assume now that there were four relevant documents, numbers 3, 7, 9 and 15. The performance in the two cases would then be as follows Coordin- Case A Case B ation R N-R Recall Prec- R N-R Level Recall Prec- Ratio ision Ratio ision Ratio 4 1 0 25% 100% 1 1 25% 50% 3 2 1 .50% 66% 3 5 z5% 38% 2 3 3 75% 50% 4 6 100% 40% 1 4 6 100% 40% 4 16 100% 20%