What type of biometric error occurred when a legitimate user is mistakenly rejected?

The situation described pertains to the scenario where a legitimate user is mistakenly rejected by a biometric system, which is correctly identified as a False Rejection Rate (FRR). The FRR measures the frequency at which authorized users are incorrectly denied access. In biometric systems, it represents the proportion of valid inputs that the system fails to recognize, thereby preventing rightful access.

This concept is crucial in evaluating the effectiveness and user-friendliness of a biometric identification system. A high FRR can lead to frustration for users and decreased trust in the system, as individuals may need to attempt multiple times before being granted access. Thus, minimizing the FRR is a primary goal in the design and tuning of biometric systems.

In contrast, the other terms reflect different aspects of biometric performance: the False Acceptance Rate refers to the likelihood of an unauthorized user being granted access, the Type 2 Error generally refers to a failure to reject a false statement in hypothesis testing, and the Crossover Error Rate represents the point where the false acceptance rate and false rejection rate are equal, which is a critical measure for assessing biometric system performance overall.