Is the Equal Error Rate a robust measure for system performance?
No. Using the threshold parameter, most practical biometric systems are not adjusted for FAR = FRR which defines the EER but for FAR << FRR. Since ROCs of different systems may behave completely different, two systems with the same EER may even differ by decades for other ROC points. To avoid such large errors, only the FAR - FRR pairs in the operating point are to be considered, e.g., by comparing the FARs at a common FRR. A consideration of the EER is only reasonable in those rare cases where the system uses the EER as operating point.
