Abstract
An expository presentation of these distributions illustrated by application to some biological and medical data. The relation between the Pascal (Negative Binomial), the Binomial, and the Poisson distributions is elaborated. The following models leading to the Pascal distribution are explained: Apparent contagion (Compound Poisson), true contagion, and random colonies (Generalized Poisson). Other contagious distributions based on the above models such as PoissonvPascal and BinomialAPoisson are presented and fitted to data on dental caries and sickness.
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