Like stratified random sampling, involves dividing up the population into groups (strata), eg age, gender, social class. The researcher is then given a number (quota) of people to research in each group (usually in proportion to the known consumer profile evident within the target market). For example, a researcher at a shopping mall may be told to interview 100 females and 150 males between the ages of 26 and 40. Once the quota for a particular group has been filled, no one else will be selected from that group. Choice over who to select for the sample is left to the researcher and it is this fact that makes quota sampling a non-random / non-probability method. This is the most common sampling method as it is relatively cheap and effective. It is a more reliable method than random as the sample is much more likely to be representative of the target population. It can, however, only be used when the profile of the target market is known.