A Double Blind Study Is One in Which _________

A double blind study is one in which _________.

A) only the patient knows if they are in the test or control group
B) only the investigator knows if the patient is in the test or control group
C) both the investigator and the patient know if they are in the test or control group
D) neither the investigator nor the patient know if they are in the test or control group
E) None of the above