vasteosuus

Vasteosuus is a statistical term used in Finnish research to describe the proportion of people who provide a usable response to a survey or questionnaire relative to the number invited or eligible. In English, the term is often described as the response rate or response share. The concept is central to survey methodology because the level of response affects the precision of estimates and the potential for nonresponse bias.

Calculation and variants: Vasteosuus is typically calculated as the number of completed or usable responses divided by the number invited (or by the number of eligible respondents). For example, if 5,000 invitations are sent and 900 completed responses are received, the vasteosuus is 18%. Some studies report multiple rates (initial response, late response, or adjusted response) depending on follow-up procedures and data cleaning.

Interpretation and limitations: A higher vasteosuus generally reduces sampling error but does not by itself guarantee representativeness. Nonrespondents may differ systematically from respondents, leading to nonresponse bias. Researchers address this with weighting adjustments, follow-up contacts, imputation, or design changes to improve response rates and reduce bias.

Applications: The term is commonly used in Finnish practice across contexts such as market research, public opinion polls, health studies, and government surveys to assess data quality and plan data collection strategies.

See also: nonresponse bias, response rate, survey methodology, sampling.