Section 9.2.5 contains examples about
how many speakers are needed to be 95% certain that the proportion
of men and women in the sample differs from that in the population
by at most 4%. In this case, the events that were being dealt with
(men and women) were equally frequent - *p* and *q* were
the same at 0.5. If *p* is quite small as it may be in the case of
impostors into speaker verification systems (perhaps less than 1% of the
users of a system), it would be
necessary to obtain very large samples (running in to tens of
thousands). In these cases the Poisson distribution has to be used
to estimate sample sizes.

EAGLES SWLG SoftEdition, May 1997. Get the book...