Interviewing all usual residents of Lithuania every time a statistical survey has to be conducted would be very complicated and expensive. For this reason, data are obtained from respondents who are randomly sampled using statistical methods. Respondents are sampled from the Population Register and the Statistical Business Register.

The sampling methods used are scientifically-based and allow making assumptions about the total population based on the data on a sampled group. The use of samples in statistical surveys enables fast data processing, reduction in survey costs.

Respondents are sampled for a statistical survey depending on the requirements for that survey. For more information about who can be questioned in a specific survey, see the section Statistical questionnaires.

Data collected using a sampling method enable the estimation of general trends characteristic of all usual residents of Lithuania. It is therefore very important that as many persons sampled as possible participate in the survey (interview) and provide comprehensive, factually correct responses.