A researcher is interested in the effect of alcohol consumption on reaction times. Participants are assigned to one of three possible conditions: nonalcoholic beer group, 1 beer group, 2 beer group. After drinking, each participant is run through a driving simulator that measures their reaction time to unexpected obstacles (e.g., a child running into the street after a ball) that randomly appear during the simulation. In this example, what is the independent variable

The Independent variable, also known as the predictor variable are variables used to influence and check changes in the dependent or predicted variable as subjects are exposed to the different types or levels of independent variable used in the study.

In the scenario described above, the predictor or independent variables which are used to measure the reaction times of participants to unexpected variables is the independent variable, beacuse these different variables ; nonalcoholic beer, 2 beer will probably affect the response time of the participants which is the dependent variable.