Separate sample logistic discrimination

The problem of discrimination when all or most of the observations are qualitative is discussed. The method of logistic discrimination introduced by Cox (1966) and Day & Kerridge (1967) is extended to the situation where separate samples are taken from each population, using the results of Aitchison & Silvey (1958) on constrained maximum likelihood estimation. The method is further extended to discrimination between three or more populations. The properties of logistic discrimination are investigated by simulation and the method is applied to the differential diagnosis of kerato-conjundivitis sicca.