Dr. goody is conducting a study of old southern university students. he has selected participants at random from a registrar's list of all students at old southern university. the registrar's list refers to what aspect of dr. goody's study?

I believe the answer is: Sampling frame.
Sampling frame refers to the list of subjects that made up the sample population within a research.
In Goody's research, the registrar;s list could be considered a sampling frame because all of his research subjects are taken from the name on that list.