[Definition of normal values in medicine]

The definition of the normal values of quantitative characters is discussed. Three distinct types of normality: statistical, biological and epidemiological, are examined. A method postulating the presence of several Gaussian components, one of which represents the truly normal population, in a heterogeneous population, is proposed for the statistical analysis of frequency distribution. Examples are given of the application of a relatively simple and effective graphical-numerical process. In the light of the preliminary results, systematic adoption of the process is suggested, not only for the definition of normal values in the sense of biological normality, but also in the comparison of patients and healthy subjects, whereby epidemiological normality can be defined by means of discriminant analysis. Lastly, the possibility of defining normal values for groups of variables is considered.