Postikyselyn

Postikyselyn is a method of data collection in which questionnaires are distributed to respondents by postal mail and returned by mail or other postal delivery methods. It is a form of self-administered survey that contrasts with interviewer-administered methods such as telephone or face-to-face interviews.

History and scope: The technique originated with the expansion of postal services and became widely used in market research, government statistics, and public opinion polling, especially before the rise of online surveys. In Finland and other Nordic countries, postikyselyt have been employed by statistical agencies and researchers to reach residents in rural areas and populations with limited internet access.

Methodology: A sample is drawn from a sampling frame such as a postal address list. A questionnaire is mailed with a cover letter, response instructions, and sometimes an incentive. Follow-up mailings can increase response rates. Responses may be returned in a prepaid envelope or via an online option. Data are cleaned, coded, and weighted to reflect the target population.

Advantages and limitations: Advantages include broad geographic reach, the ability for respondents to complete the questionnaire at their own pace, and reduced interviewer bias. Limitations include slower data collection, higher nonresponse risk, potential item nonresponse, and coverage errors from outdated or incomplete address frames. Costs of printing and postage can be substantial, and response quality can vary with literacy and motivation.

Ethics and quality: Researchers must comply with data protection laws, obtain informed consent where appropriate, minimize respondent burden, and ensure confidentiality. Weighting and imputation are commonly used to address nonresponse and measurement error.