Who Is Acting as a Confederate

Who is acting as a confederate?

A) Hannah, who thinks she has guessed what the "real" purpose of the study is and tells everyone else
B) Aisha, who signs up for every research study she can
C) Jay, who pretends to be a research participant even though he is actually working with the experimenter
D) Mikael, a research participant who decides on his own to mess with other participants