An experimenter hypothesizes that drinking alcohol will increase reaction time. After measuring people s blood alcohol levels to make sure they have not previously been drinking, she has them consume 0, 1, 2, or 3 mixed drinks. Then she has them press a button as quickly as they can each time they see an X flash on a computer screen, and measures their reaction time. In this experiment, the independent variable is _____.
whether drinking alcohol increases reaction time
reaction time
previous blood alcohol levels
whether subjects are given 0, 1, 2, or 3 mixed drinks