Ascertainment bias is a form of selection bias that occurs when certain individuals are more likely to be included in a study than others, leading to non-representative samples and distorted results. This bias often arises when the way participants are selected is related to the outcome being studied.
For example, if a survey about exercise habits only collects responses from people at a gym, it may overestimate how much the general population exercises because gym-goers are more active than average.
« Back to Glossary Index