eitodennäköisyysotannasta

Eitodennäköisyysotanta, meaning "unlikelihood probability sampling" in Finnish, refers to a survey methodology where the probability of selecting a specific unit into the sample is not predetermined or equal for all units. Instead, the selection process is designed to deliberately include or exclude units based on certain criteria, often related to their perceived likelihood of possessing a particular characteristic or being representative of a specific subpopulation. This contrasts with methods like simple random sampling, where every unit has a known and equal chance of being selected.

The rationale behind eitodennäköisyysotanta can vary. It might be employed to oversample rare populations or events to ensure sufficient data for analysis. For instance, in a study on a rare disease, researchers might intentionally select individuals with symptoms rather than relying on random selection from the general population. Conversely, it can be used to exclude units deemed unlikely to provide useful information, though this must be done carefully to avoid introducing bias.

While eitodennäköisyysotanta can be efficient for certain research goals, it presents challenges in statistical inference. Because the selection probabilities are not equal or known in advance, standard statistical formulas for estimating population parameters may not be directly applicable. Researchers must often use specialized weighting schemes or analytical techniques to account for the non-random selection and derive valid conclusions about the population of interest. The key challenge lies in ensuring that the sample, despite its non-random nature, remains representative of the target population in the aspects being studied.