What is the term used to refer to the members of the population participating in research?

The term that refers to the members of the population participating in research is "sample." In research, a sample consists of a subset of individuals taken from a larger population. Researchers typically select a sample to draw conclusions about the population as a whole, as it is often impractical or impossible to study every individual in a larger group.

A population refers to the entire group of individuals that the research aims to understand, while a sample represents only those individuals who are actually involved in the study. The terms "subject group" and "cohort" may refer to specific types of samples or groups within research contexts, but they do not encompass the general concept of participants as broadly as "sample" does. Thus, in this context, the use of "sample" accurately captures the essence of individuals actively participating in the research study.