Quota sampling is a method of sampling widely used in opinion polling and market research. Interviewers are each given a quota of subjects of specified type to attempt to recruit for example, an interviewer might be told to go out and select 20 adult men and 20 adult women, 10 teenage girls and 10 teenage boys so that they could interview them about their television viewing. ******************** It suffers from a number of methodological flaws, the most basic of which is that the sample is not a random sample and therefore the sampling distributions of any statistics are unknown.
An alternative to random sampling, often used in street surveys. For example, if each sex makes up 50% of the population, 50% of interviews must be with men and 50% with women. A random sample will get 50% of each, on average, but a quota sample will get 50% every time. Nevertheless, other things being equal, a random sample is more accurate than a quota sample.
With quota sampling, individual units in the population do not have a known chance of selection. It is a type of stratified sampling in which selection of sampling units within strata e.g. age, sex is done by interviewers on a non-random basis, controlled to some extent by quotas allocated to different strata. Each interviewer is given an assignment of interviews, specifying how many of them are to be with men and how many with women, how many with people in various age groups and so forth. These quotas are calculated from available data (e.g. Census) to arrange that, for the sampling unit (ED or town or Constituency), the sexes, age groups and social class are represented in the sample in the right proportions.
a form of sampling in which the final choice of respondents is left to the interviewers, who look for respondents based on one or two variables (such as age, sex and education) (181)
a non-probability sampling method that is constrained to include a minimum from each specified subgroup in the population, regardless of their actual probability of inclusion.
The selection of a predetermined number of elements from different sectors of the population.
A form of non-random sampling in which quotas are set for certain criteria in order to ensure that they are represented in the same proportions in the sample as they are in the population â€“ for example a simple quota might specify a 40%-60% male-female split.
A sampling method in which the final choice of respondents is left to the interviewers, who base their choices on two or three variables (such as age, sex and education). p. 183
In quota sampling, the population is first segmented into mutually exclusive sub-groups, just as in stratified sampling. Then judgment is used to select the subjects or units from each segment based on a specified proportion. For example, an interviewer may be told to sample 200 females and 300 males between the age of 45 and 60.