Finite subset of data that is chosen randomly as being representative of a population or a phenomenon to study.

### Properties

**Biased sample**

Set of individuals in a population that is supposed to represent the population, but whose selection has introduced a bias, or a source of error (positive or negative), that distorts conclusions formulated about the population studied.**Representative sample**

Sample in which the relative proportion of the variables to study is close to the proportion of these same variables in the total population.

A non-representative sample is said to be*biased*.

### Methodology

- For a sample to be representative of a population, it must have the same characteristics of this population.
- Analyzing the properties of a sample of a population makes it possible to estimate certain characteristics of this population and to determine the validity of these estimates or certain hypotheses formulated on the subject of the population that it is supposed to represent.