Seleksjonspåvirkning

Seleksjonspåvirkning, or selection bias, is a phenomenon that occurs when the selection of subjects for a study or observation leads to a result that is systematically biased. This bias arises because the sample is not representative of the population it is intended to describe. In essence, certain individuals or groups have a higher or lower probability of being included in the sample than others, and this difference in inclusion probability is related to the outcome being studied.

There are various forms of selection bias. For instance, self-selection bias happens when participants volunteer for a study, potentially attracting individuals with specific characteristics that differ from those who do not volunteer. Healthy worker bias is another common type, where the employed population used for comparison is healthier than the general population because severely ill individuals are often unable to work. Attrition bias can occur when participants drop out of a study, and their reasons for dropping out are related to the study's outcome.

Selection bias can significantly impact the validity and generalizability of research findings. It can lead to incorrect conclusions about cause-and-effect relationships or misinterpretations of population characteristics. Researchers employ various strategies to minimize selection bias, such as using randomization in experimental studies, employing appropriate sampling techniques, and carefully considering inclusion and exclusion criteria. Recognizing and addressing selection bias is crucial for ensuring the integrity of scientific research and making informed decisions based on study results.