**2.4. Performance evaluation**

A biometric system needs to be evaluated and tested; there are some measurement concepts for evaluation as equal, false rejection and false acceptance rate [1, 26]:


$$\text{FRR} = \text{(number of false rejected/NAA)} \times 100\% \tag{1}$$

$$\text{FAR} = \text{(number of false accepted/NIA)} \times 100\% \tag{2}$$

NIA means number of impostor attempts and NAA means number of authorized attempts. The accuracy and recognition rate and performance measurements of a biometric system can be affected by some factors [26]:


All the measurement rates are affected by the above factors, so any biometric system needs to calculate the error factors and tune and normalize them according to the system requirements and nature.
