FAR FRR EER – What is the BEST indicator of the accuracy of a biometric system?

Which of the following metrics is the BEST indicator of the accuracy of a biometric system?
  • False Rejection Rate
  • Crossing Error Rate (CER)
  • Equal Error Rate
  • False Acceptance Rate
The correct answer: The Equal Error Rate (EER) is the best indicator of the accuracy of a biometric system. It is the point where both the False Acceptance Rate (FAR) and False Rejection Rate (FRR) are equal. The lower the EER, the better the system is considered to be because it means the biometric system makes fewer mistakes in both falsely accepting an imposter and falsely rejecting an authorized user. The incorrect answers: While False Acceptance Rate (FAR) is an important metric for a biometric system, it only measures the likelihood of the system incorrectly accepting an access attempt by an unauthorized user. It does not take into account the system’s ability to correctly identify authorized users, which is why it is not the best overall indicator of accuracy. Similar to FAR, the False Rejection Rate (FRR) only measures one aspect of a biometric system’s performance: the likelihood of the system incorrectly rejecting an access attempt by an authorized user.
While it’s an important metric, it’s not the best overall indicator of accuracy because it doesn’t consider the system’s performance in correctly rejecting unauthorized users.

Crossing Error Rate (CER): This is a commonly mistaken term. The correct term is Crossover Error Rate (CER), which is essentially another term for Equal Error Rate.

Equal Error Rate (EER):

  • Definition: The EER is the point at which the False Acceptance Rate (FAR) and the False Rejection Rate (FRR) are equal.
  • Explanation:
    • False Acceptance Rate (FAR): The percentage of unauthorized users who are incorrectly accepted by the system.
    • False Rejection Rate (FRR): The percentage of authorized users who are incorrectly rejected by the system.
  • Significance: A lower EER indicates a more accurate and reliable biometric system. The EER provides a single value that reflects the trade-off between FAR and FRR, making it a useful metric for comparing different biometric systems.

Additional Metrics:

  1. False Acceptance Rate (FAR):
    • Importance: Indicates how often the system incorrectly grants access to unauthorized individuals.
    • Lower FAR: Higher security, but potentially more inconvenience for users.
  2. False Rejection Rate (FRR):
    • Importance: Indicates how often the system incorrectly denies access to authorized users.
    • Lower FRR: Higher convenience, but potentially at the cost of security.
  3. Genuine Acceptance Rate (GAR):
    • Importance: The percentage of authorized users correctly identified or authenticated by the system.
    • Higher GAR: Indicates better system performance in recognizing legitimate users.
  4. Receiver Operating Characteristic (ROC) Curve:
    • Importance: A graphical representation that shows the trade-off between FAR and FRR. It helps in visualizing the performance of a biometric system across different thresholds.

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