Professor Simpson is interested if time spent studying is affected by the color of a room. She randomly assigns her students into four groups and has each group study in a room that has been painted a different color (red, yellow, green, or white). Professor Simpson then measures the number of minutes that each group spends studying. What is the independent and dependent variable in this study?
The color of the rooms

The number of minutes each group spends studying

The average score each group gets on their first exam

The age and gender of the students in each group