The difference between the scholar 'pregnant dogs' and 'pets' needs no comment. If a population is defined correctly, in theory, each of its representative on the issue of the series' You buy / buy / buy / use / know / own and Prospect? " will respond positively. That such people should be enclosed in the general population, it is because they build the sample. Otherwise, the effectiveness of the study will be reduced by survey respondents unnecessary. In addition, if the analysis will be taken data from incompetent respondents, the reliability of the study will be broken.

Errors in the formation of a sampling frame can cause significant damage not less than the reliability of the results of marketing research. Sampling frame – a list of units of the population from which the respondents were selected to participate in study. If the definition of the population – is the theoretical knowledge, the sampling frame takes into account the specific features of the material items in this collection. For example, in the general population 'owners Audi cars are not older than three years' may be constructed on the basis of the sampling frame 'visitors service centers Audi'. Form a basis for sampling error occurs in the case of substitution of signs of its membership general population. All owners of Audi vehicles visiting service centers at least for the passage of the annual maintenance, so the chances to meet each of them in the service center are roughly equal. In another example, a sample of the population of owners of home computers has been constructed on the basis of a reading journal of computer topics.