Understanding the Role of Independent Variables in a Research Study

Explanation:

The independent variable in the study is the amount of red wine consumed by participants, as it is the component manipulated to observe its effect on the measured stress levels.

The independent variable in the given example, where a researcher had three separate groups of participants drink either one glass of red wine, two glasses of red wine, or no red wine to see the effect on self-reported stress, is the amount of red wine consumed by the participants. This is because the independent variable is what the experimenter manipulates or controls to observe the effect it has on the dependent variable.

In experiments, the dependent variable is what is being measured, which, in this case, is the participant's level of stress as reported on a stress measure.