Hello, based off of the following, which type of data measuring tool (Instrument) would best be used?

Research Question: Do students who spend time reading for enjoyment outside of school score higher on the reading portion of the Indiana State Reading Assessment.

Null Hypothesis: There is no difference in the reading scores on the reading portion of the Indiana State Reading Assessment of students who read for enjoyment outside of school and those who do not.

Independent Variable: Time spent by students reading outside of school.

Dependent Variable: Reading scores on the Indiana State Reading Assessment.

Instrument: ?