Why are some groups of people called "special populations" in social research? What things must a researcher do differently when studying them?

Question

Quizplus · Accepted Answer

The Answer is Some populations or groups of research participants are not capable of giving True,voluntary informed consent.
Special populations are people who lack the necessary cognitive competency to give valid informed consent or people in a weak position who might cast aside their freedom to refuse in order to participate in a study.
Students,prison inmates,employees,military personnel,the homeless,welfare recipients,children,or the developmentally disabled may not be fully capable of making a decision,or they may agree to participate only because they see their participation as a means of obtaining a desired good-such as higher grades,early parole,promotions,or additional services.
It is unethical to involve “incompetent”people (e.g.,children,the mentally challenged)in research unless a researcher meets two minimal conditions: (1)a legal guardian grants written permission,and (2)the researcher follows all standard ethical principles to protect the participant from harm.

Why Are Some Groups of People Called "Special Populations" in Social