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Biometric Technology Application Manual Section 2 13
or identity. Identification is often performed during or
immediately following the initial enrollment of the person
and may not provide an immediate result depending
on the matching speed of the technology and the number
of records being matched.
Errors and Error Rates
No biometric system can recognize a person absolutely.
While it appears to give a simple yes or no answer, it
is, in fact, measuring how similar the current biometric
data is to the record stored in the database and makes a
decision according to the probability that the biometric
sample comes from the same person that provided the
stored biometric template. While there are several types
of errors that occur in biometric systems, there are two
major classes of errors that relate to the system’s accuracy;
comparison errors and decision errors.
The errors discussed below have error “rates” associated
with them. Thus, a False Match has a False Match Rate
(FMR) associated with it, a False Non-Match a False Non-
Match Rate (FNMR) and so on. These rates are established
by extensive testing, and are nothing more than
how often these errors have been shown to occur during
testing. Expressed mathematically, a rate is the expected
probability that this error will occur in this biometric system.
These rates provide quantifiable metrics that allow
one to compare the effectiveness of various technologies
and the various products therein.
Comparison errors are erroneous matches or nonmatches
that could be considered “machine functions,”
or more semantically correct, machine malfunctions.
Version 2 – Summer 2008