Il metodo della cattura-ricattura:un esperimento didattico tra matematica e scienze naturali.

The capture-recapture method is a particular type of repeated sampling. It has been widely used to estimate the size of wildlife populations and recently it has found new applications to human populations. In this note, we illustrate both biological and epidemiological applications of the method with the purpose of supplying teaching material which could be used in introductory statistics classes. The capture-recapture model is a two sample model involving sampling without replacement from a finite population and the use of a hypergeometric distribution. First we see how the estimator of the population size can be obtained in a simple and intuitive way; we also show its equivalence to the maximum likelihood estimator. Then we propose a simulation-based activity to illustrate some important concepts in statistics: the concept of estimator, of sampling distribution and confidence interval. Varying the experiment parameters we compare different scenarios and discuss the properties of the estimators. Epidemiological applications are concerned with the estimation of the size of a hidden population such as drug users and illegal immigrants populations.