Notes on the Theory of Association of Attributes in Statistics

THE simplest possible form of statistical classification is " division" (as the logicians term it) " by dichotomy," i.a the sorting of the objects or individuals observed into one or other of two mutually exclusive classes according as they do or do not possess some character or attribute; as one may divide men into sane and insane, the members of a species of plants into hairy and glabrous, or the members of a race of animals into males and females. The mere fact that we do employ such a classification in any case must not of course be held to imply a natural and clearly defined boundary between the two classes; e.g. sanity and insanity, hairiness and glabrousness, may pass into each other by such fine gradations that judgments may differ as to the class in which a given individual should be entered. The judgment must however be finally decisive; intermediates not being classed as such even when observed.