Defining the Market Sample

To define the population to be interviewed, the question « Who do I want to interview, to whom does my market research pertain? » must be answered.

Therefore, we must necessarily determine the subject/theme of the market research, in order to define the population to be interviewed.

    The definition of this population depends on:

• the objective of market research: for example, if the market research subject/theme is “music that 15-25year-olds listen to”, the market research will obviously target young people aged 15 to 25.

• the specified claims: the actual content of the subject defines the population along one criterion or the other. For example, if the study leads to analysing the link between the type of housing (rural, urban, type of house) and the practice of sports, a limited number of towns or villages could be determined.

• the adopted/chosen sampling method: the nature of the available documents aimed at building the sample may limit the interviewed population. E.g.: the list of telephone subscribers.

    The selected criteria to determine the population can vary by:

• Descriptive criteria: age, gender, socio-professional group, geographical location, marital status, etc.

• Criteria of owned goods, consumption behaviour, extra-curricular activity practice, etc.

It is necessary to determine the most accurate sample size. Effectively, the sample must reach a minimum size in order to obtain reliable results. However, the sample size must be adjusted as accurately as possible to this theoretical size, because interviewing too many people would not be cost-effective

The sample size depends on the level of precision required: the more interviewees you have, the more precise the results will be.