In the famous Zimbardo prison study, Stanford students were assigned the role of either a prisoner or a guard so that the experimenters should examine prison life behaviors and interactions. The experiment was intended to run for two weeks but was stopped after only six days because of the brutal behavior of the guards and the depression of the prisoners. What was the independent variable in this study

Martha participates in a research study in order to receive extra credit for her psychology class. when she arrives in the research office she is given a can of what looks and tastes like beer, but which actually contains no alcohol. in the adjoining room martha's classmate karen is also participating in the study. karen receives a can of alcoholic beer. if the experiment was designed to test the effects of alcohol on concentration, then who is exposed to the independent variable?