Imagine that you are a college student who lives away from home. you have a work-study job at your college library, and you earn about $600 each month. you have one major long-term goal: you want to save up money to visit your family soon, and you need at least $100 for your train tickets.

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?