What Is an Advantage of an Active Comparator Arm? Select

What is an advantage of an active comparator arm? Select all that apply.

A) There are no ethical concerns about denying treatment to some participants.
B) Active comparator arms are very useful to no intervention arms.
C) When a well-established treatment is in common use, including it in the study is the best way to test a new treatment.
D) Use of comparators can establish how effective a treatment is over no treatment at all.