An Introduction to Statistical Measures of Biometrics

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The main aspect used to measure or evaluate the performance of a biometric system is its accuracy. From the user’s point of view, an error of accuracy occurs when the system fails to authenticate the identity of a registered person or when the system erroneously authenticates the identity of an intruder. For example, for Cars we can measure fuel consumption. Biometrics systems have their own similar performance measures unlike traditional authentication methods based on Something You Know or Something You Have.

To know if a car has a good fuel economy or not, we look at how much fuel it consumes per kilometre on average. We then compare to our expectations or some other accepted measures. Therefore, knowing what a performance measurement means is significantly important. The statistical performance measures employed for biometrics are:

  • FAR (False Acceptance Rate)
  • FRR (False Rejection Rate)
  • FTE (Failure to Enroll)
  • EER (Equal Error Rate)

False acceptance rate, or FAR, is the measure of the likelihood that the biometric security system will incorrectly accept an access attempt by an unauthorized user. For example, if Mr. A goes to a biometrics system and claims to be Mr. B, Mr. A has just made a false claim that he is Mr. B. The biometrics system then measures Mr. A’s biometric for verification. If the biometric system agrees that Mr. A is Mr. B or matches Mr. A to Mr. B, then there is a false acceptance. The reason why this can occur will be discussed in later articles.

False rejection rate, or FRR, is the measure of the likelihood that the biometric security system will incorrectly reject an access attempt by an authorized user. For example, if Mr. B goes to a biometrics system and claim to be Mr. B, then Mr. B has just made a true claim. If the biometric system does not match Mr. B to Mr. B, then there is a false rejection. The reason why this can occur will be discussed in later articles.

Failure to Enroll Rate or FTE is the measure of the likelihood that the biometric security system will fail to enrol a user. For example, Mr. A attempts to have his biometric trait enrolled. At this time, he is unable to be enrolled. The reason why this can occur will be discussed in later articles.

Equal Error Rate, or EER, is the measure of the likelihood that the biometric security system has the FAR equal to the FRR. This is a very important measure for any biometrics system. The reason why this can occur will be discussed in later articles.