Study participants are individuals who take part in research studies to help scientists gather data and test hypotheses. They can be selected based on specific criteria, such as age, gender, or health status, depending on the study's goals. Participants may be asked to complete surveys, undergo medical tests, or engage in interviews to provide valuable information. The number of study participants can vary widely, from a small group to thousands, depending on the research design. Their involvement is crucial for ensuring that the findings are valid and applicable to a larger population, contributing to advancements in fields like medicine, psychology, and social science.