Master Thesis - Department of Computer Science
Master Thesis - Department of Computer Science
Master Thesis - Department of Computer Science
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are expressed as,<br />
Gi = b GD − area(GDi),<br />
Li = area(IDi). (3.4)<br />
where area(Y ) is a function which returns area under curve Y. The lower<br />
values <strong>of</strong> Gi and Li reduce the chance <strong>of</strong> false rejection and false acceptance,<br />
respectively.<br />
• Second Criterion (C2): Second criterion utilizes the deviation <strong>of</strong> mean and<br />
variance <strong>of</strong> genuine and impostor distributions from their ideal distributions.<br />
Ideally, genuine distribution should have mean as one (1) and variance as zero<br />
(0). Similarly, for impostor distribution mean and variance should be zero<br />
ideally. Here we have considered additive effect <strong>of</strong> the deviations <strong>of</strong> mean and<br />
variance from ideal values. So goatishness and lambishness measure for i th<br />
subject is written as,<br />
Gi = (1 − µ(GDi)) + σ(GDi),<br />
Li = µ(IDi) + σ(IDi). (3.5)<br />
where µ and σ provides the mean and variance <strong>of</strong> their argument, respectively.<br />
• Third Criterion (C3): Multiplicative effect <strong>of</strong> the deviations <strong>of</strong> mean and vari-<br />
ance from their ideal values is considered as the third criterion. Here, the<br />
goatishness and lambishness measures for i th subject are formulated as,<br />
Gi = (1 − µ(GDi)) exp(σ(GDi)),<br />
Li = µ(IDi) exp(σ(IDi)). (3.6)<br />
• Fourth Criterion (C4): Fourth criterion uses the concept <strong>of</strong> performance metrics<br />
used in biometry. ZeroFRR is the lowest FAR for which no false rejection<br />
occurs. The threshold (t) corresponding to ZeroFRR, denoted by TZeroF RR, is<br />
the minimum score among the genuine scores, as FRR becomes non-zero if the<br />
operating threshold is set as greater than TZeroF RR. Let ID TZeroF RR<br />
i<br />
<strong>of</strong> impostor scores having values above TZeroF RR and can be defined as,<br />
be the set<br />
ID TZeroF RR<br />
i = {x ∈ IDi | x > TZeroF RR}. (3.7)<br />
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