a group of respondents in a quantitative study, representing a certain group/population and selected in line with precise methodological criteria.
The results of answers given by the sample are the base to forward answers to the research objectives of the study.
Research samples fall into two main categories:

• Representative - selected at random; give results which can be generalized to be true of the whole studied population;
• Non representative (non-random) - selected by other criteria; these allow for formulating conclusions solely in relation to the respondents and to assume, with unknown probability, that these results may apply to the public at large.
  The most typical non-random sample is the quota sample.