a method of sample selection for quantitative studies, where the respondents do not have to be a random representative sample, but have to meet certain recruitment criteria (E.g.  sex, age, use of specific products, etc.).
Such criteria are expressed in the form of so-called quotas - the numbers of interviews to be completed with certain types of respondents (E.g. 20 interviews with women aged 18-30, 40 with men aged 30-40 etc.).
The quotas are to ensure that the structure of the sample reflected the balance of various groups in the actual population.
In light of the non-random nature of quota samples, the results can be related solely to the respondents and assume, with unknown certainty, that these do in fact reflect the actual state of affairs in the general population.