Hi,
I don't like asking for help .. can someone check my work please ?
In a biometric system under testing there are 500 users. 200 were legitimate users (authorised), and 300 were not ( unauthorised)
At one threshold the system:-
Shut out 10 individual users it should have admitted, and admitted 2 individual it should have shut out.
What is the false rate match (FMR) at this point ?
is it 2/300 = 0.67% ???
Next the false non match rate
is it 10 / 200 = 5 % ???
If the threshold of the system is now decreased significantly which is the most liekly outcome ..
The % of false matches will increase and the % of false non matches will decrease ???
Thank you .. for your kind help and time - I do appreciate it
To check your work and find the answers to your questions, let's break down each step:
1. False Match Rate (FMR):
The false match rate is the percentage of unauthorized users that the system incorrectly identifies as authorized. In your case, the system shuts out 10 individual users it should have admitted.
To calculate the FMR:
FMR = (Number of false matches / Total number of unauthorized users) * 100
Number of false matches = 10
Total number of unauthorized users = 300
FMR = (10 / 300) * 100 = 3.33%
So, the FMR at this point is 3.33%, not 0.67%.
2. False Non-Match Rate:
The false non-match rate is the percentage of authorized users that the system incorrectly identifies as unauthorized. In your case, the system admits 2 individuals it should have shut out.
To calculate the false non-match rate:
False Non-Match Rate = (Number of false non-matches / Total number of authorized users) * 100
Number of false non-matches = 2
Total number of authorized users = 200
False Non-Match Rate = (2 / 200) * 100 = 1%
So, the false non-match rate at this point is 1%, not 5%.
Lastly, when the threshold of the system is decreased significantly:
- The percentage of false matches will increase: A decreased threshold means the system becomes more lenient, which can lead to more unauthorized users being incorrectly identified as authorized.
- The percentage of false non-matches will decrease: A decreased threshold means the system becomes more accepting, which can reduce the chances of authorized users being incorrectly identified as unauthorized.
I hope this helps you understand the answers to your questions! If you have any further doubts or need additional assistance, feel free to ask.