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. -41 - calculate fallout. A possible solution to making a full presentation of performance on a single plot is shown in Figs. 3.6P and 3.7P. Before considering these it is necessary to consider the relationship between the individual ratios of recall, fallout and precision, together with the generality number. These four ratios or parameters completely describe a given set of performance results in a retrieval table in terms of the measurements most likely to be of importance in presenting retrieval performance. However, it is only necessary to obtain any three of these in a given situation, since the fourth is then mathematically determined and can be written in terms of the other three. The four equations are:- (1) R (Recall Ratio) = ( .000 1 " -- X G P (2) F (Fallout Ratio) = t R x G P I000 - G (R x G) (3) P (Precision Ratio) = RxG (R x G) + F(1000 - G) (4) G (Generality Number) = 1000 where R (Recall Ratio) = a + .c F (Fallout Ratio)= b + d P (Precision Ratio) = a +b