Because small samples are inherently unrepresentative, it is usually not possible to
recruit a random sample for qualitative methods. Therefore, researchers select sample
members purposively or theoretically. Purposive sampling involves selecting sample members because they possess particular characteristics. For example, sample members may be
chosen because they are typical members of their category, or because they are extreme
members (e.g., heavy users or opinion leaders).
A stratified purposive sample may be
chosen so that various target group members (e.g., low-income and high-income consumers) are included or to provide comparisons between groups. Theoretical sampling occurs
when earlier interviews suggest potentially interesting participants not initially considered
in the sampling plan. For example, if discussions with parents reveal that teenagers often
have input into household technology purchases, a focus group with teens may be added to
the research plan.