The statistical variable are the qualities or characteristics of the individuals in a population.

- Qualitative variable: non numerical variables (color, marital status...)
- qualitative nominal: cannot be ordered (color, marital status etc.)
- qualitative ordinal: can be ordered (grades: A, B, C etc; Olympic medals: gold, silver and bronze etc.)

- Quantitative variable: when the variable is numerical and we can operate with it.
- quantitative discrete: the variable only admits isolated numbers (e.g., the number of possible sons)
- quantitative continuous: the variable can take any value within a certain period of time (height, distances, weight... we can always add more decimals and more precision to these variables)