Some definitions

From the research course:

External validity: Do the results hold across different settings? Can you generalise to a larger population?

Internal validity: Is there a causal relation between two variables? (no confounds)

** What does confounds mean in this context?

** What do we mean by power of a statistic?

The NIST speaker recognition evaluation: Overview methodology, systems, results, perspective.
Doddington, G.R., Przybocki, M.A., Martin, A.F., and Reynolds, D.A.
Speech Communication, 2000, 31(2-3), 225-254.

Identification: Deciding amongst a set of candidates who the biometric belong to.

Verification: Whether the biometric belongs to a particular candidate.

Closed set identification task aka closed world assumption: When actual subject is always one of the candidates.

Open set identification task: When actual subject may not be one of the candidates.

Sheep: well behaved subjects who dominate the target population.

Goats a minority group who tend to determine the performance of the system through their disproportionate contribution of errors.

Wolves are imposters who have unusally good success at impersonating many different target speakers.

Lambs are target speakers who seem unusually susceptible to many different imposters.

Weighted detection cost function:

Cdet = cmiss . Emiss . Ptarget + cfa . Efa . (1 – Ptarget)

cmiss and cfa are the relative costs of detection errors

Ptarget is the a priori probability of the target