In this paper we propose a reject rule applicable to a Multi-Expert System
(MES). The rule is adaptive to the given domain and allows the achievement
of the best trade-off between reject and error rates as a function of the c
osts attributed to errors and rejects in the considered application. The re
sults of the method axe particularly effective since the method does not re
ly on particular statistical assumptions, as other reject rules. An experim
ental analysis carried out on publicly available databases is reported toge
ther with a comparison with other methods present in the literature.