1. Statistical distributions and related representations

Definitions: we call :

• • individual, unit of observation (e.g. company, production line);

  • population, the set of individuals concerned by the study (e.g. all French companies, all parts leaving the production line);

  • sample, a subset of the population whose individuals will be studied. The choice of sample is made according to certain rules;

  • variable or statistical character, the aspect of the statistical unit we're going to study (examples: geographical location of the company,...