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The false acceptance ratio (FAR) is a unit used to measure the average number of false acceptances within a biometric security system. It measures and evaluates the efficiency and accuracy of a biometric system by determining the rate at which unauthorized or illegitimate users are verified on a particular system.
FAR is also known as false acceptance rate or type II error rate/ratio.
FAR primarily helps determine the accuracy level of a biometric security system. FAR is calculated by dividing the number of false acceptances by the number of identification attempts. So,
FAR = FA ÷ TA
FAR = False Acceptance Ratio
FA = Number of False Acceptances
TA = Total Number of Attempts
For example, if the number of false acceptances is 100 out of a total of 1,000 identification attempts, the FAR is 0.10. This means that the biometric system will allow 10 percent, or 1 out of each 10 false attempts, to access the system.