this artist is an incredibly good pianist and singer. she is a performer, songwriter, and producer. her influences include madonna, david bowie, and freddie mercury. her name is stefani germanotta, but we know her as .

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?