How is the sample selected for the aforementioned methods? Sampling is a procedure which selects a smaller number out of a larger population (e.g. all citizens of a country or all elected mayors in one region) in such a way that the selected units, persons, geographical areas, etc. are sufficiently typical or representative of the larger population. Sampling involves deciding how many units to include in the sample and how to select them. Details of how the samples would be constructed are discussed with the client.
The key strength of focus groups is that it enables development of opinions and responses which are typical for a particular group. This means it is usually desirable that the groups are homogeneous with respect to socio-demographic variables, i.e. there is little variation within the groups. Therefore, with focus groups, sample construction is a question of ensuring that the groups themselves, rather than the individuals within them, are as representative as possible of the desired population.
In many cases, a simple random sample is not possible or desirable and, thus, a more sophisticated sampling techniques are used, such as stratified sampling or cluster sampling. We use specialised software to prepare and analyse these kinds of samples.