CRANV2 Main test 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. - 81 - It will be seen from Figure 4.001 that, at a coordination level of 6, only 161 of the possible 164 questions were searched, and from this stage there is an increasing disparity between the figures in column y and z. Column x shows the number of questions that were able, at any given coordination level, to retrieve any documents, whether relevant or non-relevant. It will be noted, for instance, that it was not until the coordination level had dropped to ten terms was it possible to retrieve a single document; at this level, as can be seen from the figures in columns x and z, of the 52 questions having ten or more starting terms, 6 questions retrieved documents. (11) In the columns of documents retrieved are shown the total numbers of relevant and non-relevant documents retrieved at the various coordination levels. These figures have been obtained by summing the results for each individual question in the question set. As mentioned in the previo[OCRerr],s section, in some cases the searches were not completed at the lower coordination levels. The result is that the figures for non-relevant documents retrieved are estimated by a method described on page 28. All such estimated figures are indicated by as asterisk. However, it should be noted that the figures for the retrieval of relevant documents are always correct. (12) The actual performance measures presented in the tables are recall ratio, precision ratio and fallout ratio. These are derived from the following:- a. Relevant documents retrieved b. Non-relevant documents retrieved c. Relevant documents not retrieved d. Non-relevant documents not retrieved Recall ratio is 100a that is relevant documents retrieved over a + C ' the total relevant. All such figures in the tables are correct, but ( 100a : for precision ratio [OCRerr]1 and fallout ratio (100b) , it was in some cases necessary to use the estimated figures discussed in the previous section. Where this has been done, an asterisk is placed against the figure in the table. TABLE OF RESULTS The tables of results are presented in nine main sections. Details are given before each section of tables, but the following is a brief resume.