Final answer:
The hours slept is the independent variable, while the test grade is the dependent variable.
Step-by-step explanation:
In this experiment, the hours that students slept is the independent variable, while the grade they got on the test is the dependent variable.
The independent variable is the one that is manipulated or controlled by the researcher. In this case, the researcher is testing how the number of hours students sleep affects their test performance.
The dependent variable, on the other hand, is the variable that is measured or observed and is affected by the independent variable. In this case, the dependent variable is the grade the students receive on the test, which is influenced by the number of hours they slept.