Probabilistic samples are those in which all elements of the population have the same probability of being chosen or selected. Non-probabilistic samples involve the choice of elements, not based on probability but on causes related to the characteristics of the researcher or research. They allow you to measure the level of error in predictions. All elements of the population have the same option of being elected. The sample is obtained by means of a calculation of probabilities that allows to eliminate arbitrariness with a random or random determination. A systematic selection procedure (tables of random numbers, for example) is used to ensure that the entire population has had the same opportunities to be elected. The sounding base (list from which the sample is selected) is essential. They are usually used for surveys, content analysis (quantitative methodology).

The probabilistic samples can be:

               Simple random samples

   Systematic random samples

   Stratified samples

   Aggregated samples