**3.7. Performance evaluation of biometrics systems**

Different measurements can be used to evaluate the performance of biometric systems. The most famous measurement is the recognition rate, which is defined as the percentage of the samples that are correctly matched samples to the total tested samples. Another popular measurement is False Reject Rate (FRR) versus False Accept Rate (FAR) at various threshold values, where FRR refers to the expected probability for two mate samples which

**Figure 6.** Block diagram of a speech recognition system.

are wrongly mismatched and FAR refers to the expected probability that two non-mate samples are incorrectly matched.

Single-valued measure "Equal Error Rate (EER)," that is threshold independent, can also be used to evaluate the performance of recognition systems. EER is the value, where FRR and FAR are equal.

Detection Error Trade-off (DET) or Receiver Operating Characteristic (ROC) curves are also used to compare the performance of biometric systems in which both curves plot FRR against FAR in the normal deviate and linear scale, respectively.
