What needs to be considered in the definition of FRR?
Even though the false rejection rate, FRR, is intuitively easy to understand, there can be many problems when trying to fix an unequivocal or universal definition. The following must be taken into account: • The FRR is a statistical value whose measurement accuracy depends on the number of measurements. Now the FRR is not only dependent on the biometric system, but on the users as well. There is thus a personal FRR. If one wants to deal with large numbers of people, it is important that the end result is not negatively affected by an individual. Such could occur when the number of attempts per person differs. This problem can be avoided, if one first identifies each personal FRR curve and calculates the mean from those (or uses the median, but this provides different values!). • The exact meaning of rejection must be clarified. Here for example, the total number of recognition attempts before the final assessment of a failed recognition play a role. There are systems, which can continu
