Dr. Branch would like to study the relationship between room lighting and college students' test performance. He randomly assigns college students to two groups. The first group takes an exam in a dimly lit room and the second group takes the same exam in a regularly lit room. What is the independent variable?

Answer: Room lighting is the independent variable (light intensity)

Explanation:

An independent variable is one that can stand on it's own. It does not rely on the other variable. It cannot be altered by the other variable you want to measure. In this case, you are trying to see if the independent variable which is the light intensity can cause some obvious changes in the dependent variable.