SP500207 Appendix A: TREC-1 Results appendix National Institute of Standards and Technology Donna K. Harman Box 4-- ROC Averages lines 1-10-- The average prohability of detection (recall) at a fixed probability of false alarrn rate (fallout). Ten equally spaced false alarm points in the high precision end of the curve were used, and for each topic, the highest detection value in the region surrounding that false alarm point is selected. The table shows the averages of these points across all topics. Graph 1-- Recall-Precision Curve This is a plot of the data shown in Box 2. Graph 2-- Norrnal Deviate - Detection-False Alarm This is a plot of the data shown in Box 4, but plotted on probability scales. See Overview, section 42 for a reference explaining these plots. 374