What is the difference between selection bias and self-selection bias?

Selection bias is a broad term used to describe different situations in which the selection of study participants leads to an error (bias). As a result, the study population is not representative of the target population. Usually, selection bias is a result of an error in the study design.

Self-selection bias is a subtype of selection bias. It specifically refers to research bias caused by study participants themselves and occurs when individuals volunteer to be part of a research study.