Sampling problems for focus groups are of three types – how many different groups to have; how many people to have in each group; and what the makeup of each group should be. A generally accepted rule of thumb is never to use only one focus group. The guiding concept is to keep running groups until the researcher is getting no more new ideas. In practice, three or four groups on a given topic are typical.
Six to 12 people in a group has come to be the rule of thumb, in the field. Tests have shown groups of 8 produce more and better ideas than groups of 4, but there is no objective that shows 8 is better than 20. Moderators find groups of more than 10 or 12 difficult to manage in the way they believe desirable.
Individuals for the focus are selected on a quota basis with the market for the product and the purpose of the research the determining factors in the quotas. In almost all cases it is desirable to have individuals who have had experience with the product in questions and are articulate. Therefore, product and brand usage and frequency of purchase are often the basis for selection to the group.
The one or few segments most important for the project should dominate the sample. It is often useful to have different focus groups for different important market segments rather than to have several segments represented in the same group. While the interaction among the different segments may be useful, it often leads to so much variation that no clear ideas develop. Some researchers, for example, don’t have full time housewives with children at home in the same groups as working women without children because their life styles are completely different. Some practitioners never have men and women in the same focus group because they believe there is more performing when the two sexes are together.
Strangers in focus groups are believed to feel less inhibited and, thus to express more freely their attitudes and behavior. For this reason efforts are often made to have each focus group composed of individuals who do not know each other.
Organizations specialize in recruiting participants for focus groups. They usually have lists of organizations such as PTAs or religious groups from which volunteers can be obtained. They call names on these lists and screen them according to the quotas established. When difficulties are encountered in filing certain hard-to-find quotas, these recruiters may resort to recruiting friends or pushing individuals into categories other than those in which they naturally fall. Many people enjoy focus-group experiences and try to get into such groups frequently, but experience has shown that participants cease to react spontaneously if they are in more than one or two groups a year.
It must also be remembered that the individuals, usually women, who participate in focus groups are probably from a segment of the population that is more outspoken, more activist, more domineering than other women. Whether this means they are different in consumption attitudes and habits is not clear.
Example: An exploratory study of the quality of business services concentrated on four specific services. Focus groups were used as follows:
A total of 12 focus group interviews were conducted three for each of the four selected services. Eight of the focus groups were held in a metropolitan area in the southwest. The remaining four were conducted in the vicinity of the participating companies’ headquarters and were therefore spread across the country one on the West Coast, one in the Midwest, and two in the East.
The focus groups were formed in accordance with guidelines followed in the marketing research field. Respondents were reviewed to ensure that they were current or recent users of the service in question. To maintain homogeneity and assure maximum participation, respondents were assigned to groups based on age and sex. Six of the 12 groups included only females. At least one male group and one female group were interviewed for each of the four services. Consistency in age was maintained within groups; however, age, diversity across groups for each service category was established to maintain the view points of a broad cross section of consumers.