Cesar Recently Participated in a Social Experiment Examining the Effects

Multiple Choice

Cesar recently participated in a social experiment examining the effects of crowds on self-esteem, but was unaware of which group he was assigned to. Cesar was later informed that the social psychologists responsible for the study were also unaware of Cesar's group assignment at the time of the study. This is an example of:

A) a single-blind procedure.
B) a double-blind procedure.
C) a repeated measures design.
D) a planned contrast.