Dr Smith Is Instructing His Graduate Students to Put Together

Multiple Choice

Dr. Smith is instructing his graduate students to put together a sample for an upcoming research study of college students. The graduate students were asked to stand outside of the student union to solicit participants, finding 50 freshmen, 50 sophomores, 50 juniors, and 50 seniors. What sort of sampling method is being used?

A) Simple random sampling
B) Quota sampling
C) Cluster sampling
D) Stratified sampling
E) Accidental sampling