Biometric terms: Part 1

Welcome to the first instalment of our blogposts about the terms we use in our tests and the ones you may come across when dealing with biometry. Our aim is to make these words, terms and abbreviations understandable and defined in layman's terms, based on the respective standards. Part 1 is dealing with the abbreviations and words regarding performance and enrolment.


The False Rejection Rate is a metric that shows how many legitimate identification attempts were rejected by the system, including the occasions where the device failed to detect the identification attempt.


The False Non-Match Rate is a metric that shows how many legitimate identification attempts were rejected by the system. Note, that for most of our tests, we use this metric along with FTA to give a better and more accurate picture about the device performance.


The False Acceptance Rate is a metric that shows how many illegitimate identification attempts were accepted by the system. FAR is generally calculated and tested during algorithmic tests, as it is rather hard to measure empirically, as one would need a large body of test samples to create a statistically significant result during scenario or operational tests.


The Failure To Acquire is a metric that shows how many attempts were that the system did not detect at all. Note, that the duration of time that must elapse until the attempt can be considered FTA may differ from device to device, but a 10 second limit can be considered adequate for this purpose.


The Average Recognition Attempt Duration is a metric that shows the average time of identification and/or rejections of a biometric identification system. Note, that in order to talk about ARAD, the device must first successfully capture the sample, thus FTA durations are not considered in this value.


The enrolment of a user is the process when a user ID is created and the user sample is first taken. In other words, this is the occasion when the user is introduced (and taught) to the system. An enrolment may consist of several enrolment attempts which themselves can consist from several enrolment actions.


The Average Enrolment Transaction Duration is a metric similar to the ARAD, however, this metric is for enrolments. It shows how much time is required for a successful enrolment of a user, which may consist of several enrolment attempts.

Enrolment action

An enrolment action is performing a single enrolment tasks within a device (e.g. positioning the hand once in a hand geometry reader). Different devices may require different amounts of enrolment actions, e.g. most fingerprint readers require two actions (placing the sample on the reader twice - or more if the device is unsure).

Enrolment attempt

An enrolment attempt is a single round of enrolment actions that will either result in successful or unsuccessful enrolment of the user.


The Failure to Enrolment is a metric that shows the amount of times where the user can not be enrolled in the device at all. The amount of enrolment attempts after which an case can be considered FTE is arbitrary, and has to be defined in every situation with respect to the devices. For example, it is reasonable that one may try to enrol a user 2 or 3 times in a system, before declaring the case as an FTE, but under most circumstances, 10+ attempts are unreasonable.

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