What is essential when comparing the ROC performance of biometric systems?
The accuracy performance of a verification system can be determined by exactly three statistical quantities: FAR, FER, and FRR. Since these three quantities influence each other when parameters (e.g., quality acceptance thresholds for enrolment and authentication) are changed, a comparison of one quantity between two systems makes only sense when the other two quantities are mutually equal. For example, let the FARs of different systems be compared. Then the corresponding FRRs must be equal, and the FERs must be equal, too. Regarding a ROC diagram, this condition can be easily fulfilled for all FRRs for which the curve has been measured, provided that the FERs of all curves are constant and the same. However, this is often violated since the FERs are actually different! A solution to this problem comes from the procedure used, e.g., in the Fingerprint Verification Competition FVC2002, where different algorithms for fingerprint recognition have been tested. The idea is to consider a fai
